An insular, agoraphobic boy named Wataru Kurenai begins his battle against the Fangire as Kamen Rider Kiva, a battle with connections to a conflict from 22 years in the past...

In 1986, Yuri is ordered to protect a violinist who is likely to be targeted by a Fangire and also happens to be a student of Wataru’s father Otoya. Meanwhile, in 2008, Wataru continues to try and figure out how to make a violin that will equal his father Otoya’s, as he finds himself repairing a violin damaged 22 years earlier…

In 1986, Oyoya flirts with several women before Yuri arrives and they are attacked by a Fangire, where Otoya shows prowess fighting back and generating interest in him by Yuri’s boss. In 2008, Wataru is approached by a lawyer who details accusations against his father and victims of his crimes, forcing him to find one good thing Otoya did in the past to resolve matters with the people who were wronged.

As Yuri continues her investigation of Otoya in 1986, she reports back to Shima, who decides to pass on bringing Otoya into their group. In 2008, Wataru works to atone for his father’s crimes, but he discovers someone who refuses to ever forgive Otoya as she transforms into the Moth Fangire!

After a disastrous attempt to try to warm his neighbors up to him with a violin performance, Wataru pleads with Nago to help him become more confident. Nago tasks him to trail Megumi as her bodyguard, but he finds himself working with a strange man claiming to also be working for Nago!

As a bizarre Fangire attacks mother and daughter in both the past and present, both Otoya and Wataru must save their respective female targets before the Fangire is able to make them his bride!

In 1986, Otoya joins Yuri in tailing Jiro to investigate missing customers from Mal d’Amour, while in 2008, after leaving the hospital, Megumi invites Wataru on a date as cover while she investigates Maison Cercueil, but Nago interferes once again…

Megumi attempts to force Wataru’s attention away from Nago to prevent him from being manipulated as the investigation into the French restaurant continues while in 1986, Otoya tries to solve the mystery of the cafe victims as Jiro continues his attacks.

Wataru gains the assistance of a violin maker in trying to create an instrument that fits who he is while in 1986, Yuri and Otoya try to decipher the curse of a violin and a monster attacking those who possess it. In both the present and the past, talk of the IXA System leads to the appearance of another Rider on the battlefield…

As Wataru learns of Oomura’s promise from 22 years ago and his history with Wataru’s father, back in 1986, Otoya confronts Jiro about the monstrous transformation he witnessed but while following him and Yuri, he ends up face to face with Oomura as the men discuss the craftsmanship of their violins…

Wataru discovers rock music when he’s asked to help a musician with his band while in 1986, Yuri tries to position herself to become the first IXA in order to take revenge on the Fangire that took her mother.

As Yuri demands to know why Jiro was chosen for IXA over her, she learns of the cost of using the still-incomplete system while in 2008, Wataru is injured after the attack by Nago, causing him to struggle with his role in the band…

As Jiro vows to rebuild the Wolfen race, Otoya protects a woman and is severely beaten by him, but in the commotion, Jiro loses the IXA Knuckle, and Oyoya seizes the opportunity. Meanwhile, Wataru continues to help Kengo to achieve his dream while Nago struggles with his loss to Kiva…

After driving Jiro back, Otoya suffers from the side effects of the incomplete IXA System, but he puts on a front to deflect suspicions by Yuri. In 2008, Wataru pleads with Kengo to abandon the mysterious promoter, who he now suspects is a Fangire, but Kengo won’t listen…

After Otoya is knocked out during his fight with Jiro, Yuri recovers the IXA Knuckle and plans to track down the man who murdered her mother. But when she faces the man, she is swiftly knocked out as Jiro arrives and also recognizes him… as the man who slaughtered the Wolfen race. He is Rook, of the Fangire’s Checkmate Four! Meanwhile, in 2008, Wataru and Shizuka encounter Rook, who seems to be suffering from amnesia…

As Wataru and Shizuka try and help Rook, who they’ve nicknamed “Biggie”, recover his memories, he begins spending time with a young woman whose bike he helped fix. Their hope is this might jog his memory. Meanwhile, Jiro proposes an alliance with Otoya to take down Rook and protect Yuri, and Otoya tenuously agrees…

Otoya is tasked with helping a young girl pass an audition, being promised a date with Yuri in exchange. In 2008, Wataru meets an archer named Mami, who takes him under her wing, while Nago angrily pursues a criminal that is also the Seastar Fangire…

Convincing his student that her slump is due to her not playing from the heart, Otoya gives her the confidence she needs to not only pass the audition but to realize where her heart truly lies. In 2008, Wataru loses his resolve to fight, but when he discovers that Mami has been injured by the Fangire, her pep talk about doing what his heart tells him inspires him to remember why he battles the Fangire…

In 1986, Rook begins to target women getting married, and Yuri finds herself face to face with him when he shows up at a wedding she was attending. After his attack, she begs Jiro to let her use IXA, but he continues to refuse while Otoya creates a distraction and steals the IXA Knuckle. Meanwhile, in 2008, Wataru meets with Kengo once more, who is convinced that Kiva will be his inspiration for his music. But when they attempt to learn more about Kiva, Wataru finds himself out cold as his body is suddenly inhabited… by his father?!

As the Ladybug Fangire escapes from the Otoya-possessed Wataru, it takes Kengo and Keisuke as hostages to force Megumi into a fight as IXA. As “Otoya” tries to teach her about the resolve needed to be a warrior, she refuses to listen, and time is running out for the hostages. Meanwhile, in 1986, the actual Otoya runs into a mysterious woman at a wedding while looking for Yuri, who is revealed to be the queen of the Checkmate Four, Maya…

After Yuri treats Otoya to a meal to thank him for what he did during the wedding incident, Jiro becomes angry at Otoya’s affection for Yuri, prompting Jiro to propose to her! Stunned, she isn’t sure whether to accept, but Shima thinks it’s a good idea. In her frustration, Yuri sets up a group date where Otoya runs into an old friend. Meanwhile, in 2008, Kengo suggests to Nago, Wataru, and Megumi a group date of their own, where things go poorly, including the antics of a clumsy waitress…

As Otoya works to help Yumi gather money, the Luxur store manager continues to attack patrons, until Shima explains what’s been going on and a trap is set to catch the Fangire. In 2008, Wataru learns the name of the awkward waitress he met before, and after running into her again, the pair hit it off as Mio asks Wataru on a date.

In 1986, Ramon and Riki’s massage parlor is shut down for operating without a permit, so Jiro arranges for them to work at Mal d’Amour, leading Otoya to give Riki advice on love. Meanwhile, Maya is continuing to eliminate Fangires who have fallen in love with humans, but one Fangire named Shinji manages to escape her as he struggles with his relationship. In 2008, Megumi convinces Mio to model with her when one of the other models is ill, leading Wataru into a confrontation with the Grizzly Fangire!

After Jiro’s attack, Otoya is rescued by Ryoko and Shinji, who nurses him back to health, and he inadvertently repays the favor when he interrupts Maya as she’s about to eliminate Shinji. At the same time, Jiro has taken Yuri hostage and loses control, madly declaring that she’ll be his forever, but the admission she makes shocks him. In 2008, as Ryoko’s illness takes a turn for the worse, Shinji takes her to the tree they planted 22 years ago, but when Nago confronts him, he flips into a rage and attacks Mio, upsetting Wataru and unleashing a new power…

With Jiro’s disappearance, Yuri supports Otoya’s induction into the Wonderful Blue Sky Group as IXA’s official user. But when they plan to seek out her mother’s lost ring, Otoya finds himself suffering memory loss after a battle with Rook, when Maya, the Fangire Queen, arrives and claims to be Yuri! Meanwhile, in 2008, Wataru finds Mio has distanced herself from him after an encounter with Bishop, another member of the Checkmate Four!

Continuing to take advantage of Otoya’s memory loss, Maya attempts to learn more about human love as Otoya searches for the lost ring. But when Yuri finds them, she may have to be the one to explain it to the Fangire Queen! In 2008, Wataru worries about Mio’s whereabouts as she hides from her duty as Queen. With Bishop demanding her obedience, she turns to Wataru for help, but gets ambushed by the Spider Fangire, who has stolen the IXA gear!

Nago offers his resignation to Shima, but Shima refuses, granting him access to IXA’s Rising upgrade as he feels Nago has accepted his own weaknesses. However, the celebration is short-lived when Megumi and Shima are arrested. Nago is informed by the senior officer responsible that his former dealings with the Blue Sky Group 22 years prior led him to be injured by IXA, and in order to save his colleagues, Jiro appears and grants Nago access to Castle Doran’s Time Door, sending him back to 1986 and bringing him face-to-face with Otoya!

Still in 1986, Nago tries to explain to Tanahashi that he’s from the future and trying to change history, but Tanahashi believes he’s lying. After Nago attempts to throw Otoya off by kidnapping Yuri, Maya saves him and asks about human love, and while Nago can’t explain it directly, he gives her the button from his first bounty, calling it a good luck charm. Later, when the events leading to Tanahashi’s injury begin to unfold, Nago changes the future and vanishes, but upon his return, after assisting Kiva, he discovers that Wataru holds the very button he gave Maya! But why does Wataru have it?

As Yuri cleans Otoya’s house, she worries about feeling happy when Rook is still on the loose, reaffirming her desire to defeat the powerful Fangire, but Jiro has his own revenge plans and enlists the help of Otoya to plan a four-way attack with Ramon and Riki while keeping Yuri in the dark. In 2008, Wataru reconciles with Mio, but Bishop refuses to accept these circumstances while Megumi is approached by her brother, who makes a donation to the Blue Sky Group in order to force her to return home to her family.

Having been attacked by Rook, Yuri is nearly killed before Jiro manages to intervene, landing her in the hospital. Jiro and Otoya visit her, telling her not to rush back into action, but she rushes out, falling for their diversion as they bait Rook once more. In 2008, Wataru’s relationships are increasingly strained, with Kengo upset by Wataru’s lie about his recovery, and Mio once again rejecting Wataru due to Shizuka’s meddling. With her brother still demanding Shima relieve her, Megumi goes undercover to tail a Fangire target, and when IXA and Kiva enter battle, Nago makes a shocking discovery…

In 1986, Rook enjoys his reward for beating IXA and the monsters as Yuri steals the IXA Knuckle and rushes to Rook, who steals the Knuckle and transforms into IXA! The monsters fight back, but Rook overpowers them easily as he runs wild. But when IXA overloads, Otoya and the others reveal their plan, as Yuri becomes IXA to finish off her mother’s killer. Meanwhile, in 2008, Nago discusses Wataru’s role as Kiva with Wataru, who he takes on as his pupil, further upsetting Kengo. As Bishop pushes Mio further into her role as Queen, Megumi discovers her mother’s notes on Rook and begs Nago to lend her IXA in order to exact her revenge…

In 1986, Yuri is happy after defeating Rook and suggests marriage to Otoya, who is taken aback. Soon after, he runs into Maya, who is playing the violin and poses a question to him about her playing before she leaves to visit her infant son. But when Riki attacks her as she visits Otoya to see if he knows the answer to her question, her role as Fangire Queen is revealed! In 2008, Wataru finds an injured Mio, and the two patch one another up, both unaware as to one another’s roles, while Taiga, Wataru’s first friend, and the Fangire King, reappears!

After Maya defeats Dogga, she is surprised that Otoya has remained in spite of her true identity as a Fangire. She asks him once more for the answer to her question as she offers to help him construct a violin able to bring out his true talent. As they work side by side, Yuri watches with a pained heart as Otoya grows closer to the Fangire Queen. In 2008, Saga watches Kiva’s battle before retreating, while Wataru promises to stay by Mio’s side as the battle concludes. However, when Wataru discovers that Taiga’s fiancee is Mio, Wataru is crushed, despite Mio’s assurances that the pairing was arranged.

Wataru celebrates his broken heart as he tries to move on from Mio, but it doesn’t seem like that will be easy as he still finds himself spending time with her and Taiga. While at an amusement park, an escaped prisoner takes a hostage and Nago attempt to defuse the situation but the newest member of the Blue Sky Group intervenes. It’s Kengo! And he’s sporting a new look and a new attitude, disrespecting both his former friend and his ex-mentor. Meanwhile, a scientist works to infuse one Fangire with the stolen powers of other Fangires, and Mio seeks an audience with Maya to come to terms with her role as queen…

With the Bloody Rose complete, Otoya plays it for the first time for Maya, blessing it with a prayer to preserve music for all time. Yuri, fed up, runs off and encounters Jiro, who learns of the strange relationship between Otoya and Maya and confronts him about it. In 2008, with the Bloody Rose damaged due to Wataru’s state of mind, he attempts to fix it, but it lacks something that gives it power. Meanwhile, Mio begs Maya to release her from being Queen, but Maya explains that the power itself chooses the Queen, while Kengo is given the IXA Knuckle to Nago’s dismay.

Bishop begins the preparations for the wedding of Taiga and Mio, but Mio admits she is in love with someone else and can’t go forward, enraging Taiga. Not realizing it is Wataru she loves, Taiga enlists the help of Wataru, who is himself blind to Mio’s true feelings, to try and determine who she has feelings for. When she meets with Kengo in the park, Taiga confronts her as Kengo attacks Wataru, but Jiro brings Watary back to Castle Doran to observe a mysterious sword embedded in the wall, said to be extremely powerful…

Mio reveals her feelings for Wataru as Taiga lurks nearby, discovering the truth for himself. As Wataru basks in his happiness, Taiga confronts Wataru and invites him to Mio and Taiga’s wedding, telling Wataru he’s always been weak. Jiro brings Wataru back to Castle Doran, suggesting he try once more to claim the Zanvat Sword by wishing for its power from his heart. Meanwhile, in 1986, Yuri confronts Maya, but Maya refuses to attack, knowing she’s taking something far more precious from her…

Mio and Wataru discover one another’s identities, along with Taiga realizing that as Kiva, Wataru is his half-bother. In denial, Wataru runs off, collapsing in the woods. Taiga decides to go speak to Maya to demand answers, while Nago attempts to coach Keno in the use of the IXA System, but his efforts don’t end well. In 1986, Otoya visits Yuri and tells her he intends to find Maya, while the Fangire King is confronted by Jiro as he summons a dark version of Kiva to finish off the Wolfen for good.

Jiro fights a losing battle with the Fangire King, who has also tracked down Ramon and Riki to eliminate them all Arms Monsters, but the trio narrowly escape and run into Maya and Yuri, demanding that Maya act as a shield for them, but she quickly dispatches them, revealing to Yuri that she is a Fangire. Shocked, she confronts Otoya, who calmly says he knew, enraging Yuri. In 2008, Wataru questions his half-Fangire heritage and requests a meeting with Shima and the others to reveal his secret, telling them he intends to be the bridge between humanity and Fangires.

Now aware that Maya is a Fangire, Yuri encounters her once more and intends to kill her, but Otoya stops her, suggesting a picnic, but she storms off. Maya takes her place, and afterward, Otoya passes the Fangire King, who tracks down the Arms Monsters and agrees to spare them if they’ll kill Otoya. In 2008, having regained his senses after Bishop released his Fangire nature, Wataru relapses into isolation as he fears that he’ll hurt another human, while Nago regains the IXA Knuckle, but finds himself facing Taiga as Wataru ignores the Bloody Rose’s call for Kiva…

The Arms Monsters attempt to eliminate Otoya in order to be spared by the King, but none of them can go through with it and the trio decides to split up and run, but they don’t get before the King uses his dark Kiva powers to seal them into the weapons Wataru will use in the future, imprisoning them in Castle Doran. In 2008, Shima fires Kengo, who begs Wataru not to give up with Nago and the others, but Wataru won’t budge. But when a vision of Maya comes to him in a dream, will he find his resolve to believe in himself?

In 1986, Otoya battles Dark Kiva with IXA but is hopelessly outmatched and is taken prisoner by the King, intending to feed him to Castle Doran. Maya pretends not to care, but she seeks out Yuri and begs her to help rescue Otoya after she admits she is in love with him. Yuri agrees, and the two enter the Lost Woods, where Castle Doran sleeps. In 2008, Taiga is upset by Wataru’s decision to fight for humanity, pointing out they’ll end up fighting one another eventually. As Shima visits Yuri’s grave, he is attacked by a Fangire and gravely wounded, but Taiga offers Wataru a way to help him…

In search of Otoya, Yuri and Maya battle the Silkworm Fangire as Otoya’s life is drained into Castle Doran. As time is nearly up, he requests that the King allow him one final performance, playing a song to act as a beacon for Maya and Yuri. As they escape with him, Otoya dons IXA to defeat the Silkworm Fangire while Maya is stripped of her powers. In 2008, Shima acts strangely as the Sungazer Fangire appears, but everyone is stunned when it changes back into Shima! Meanwhile, Taiga and Mio begin the wedding ceremony, but Mio has plans of her own…

In the aftermath of Mio’s death, Wataru confronts Taiga until Jiro drags him to the Time Door, hoping that Wataru will regain his composure if he meets his father. But when Wataru returns to the past, he is hellbent on saving Mio by erasing his own existence and keeping his parents from getting together. When he is forced to reveal his parentage, Otoya is unable to believe it, but he slowly comes around until the two are attacked by a Fangire, leading father and son to fight side by side.

After Wataru rescues Otoya, the King reveals his true Fangire form and attacks, but Otoya escapes and encounters Kivat-bat the 2nd, who tells him that Maya sends a message: they can never meet again. If they do, the King will kill Taiga, who he is holding hostage. Disgusted by his actions, Kivat-bat the 2nd proposes a pact with Otoya, granting him the Dark Kiva powers at the risk of his life! In 2008, Taiga agonizes over Mio’s death until Bishop reveals Wataru did not kill her, he did, in order to send Wataru into despair. Taiga reacts violently, angering Bishop into acting on his own, plotting revenge…

Wataru battles the Bat Fangire after his father is injured, but he’s no match for the incredible power wielded by the King. Enraged, the injured Otoya switches to IXA, but the weaker prototype is easily dispatched by the King, as the IXA armor shatters. Despite knowing that using Dark Kiva again will mean his demise, Otoya transforms and the two Kivas stand side by side and finally destroy the King. Otoya begins to die but puts on a brave facade as his son fades away, returning to the future he came from. Back in the future, Wataru exudes new confidence while Nago fights Bishop but is severely injured in the process…

Taiga and Wataru resume their fight after eliminating Bishop’s revived Fangires. With the embracing of his Fangire side, Wataru defeats Taiga and tells his brother he refuses to help him. While Bishop’s plans to revive the previous King continue on, Taiga visits Maya after she refuses to grant him the power of Dark Kiva, he attacks her and obtains Kivat-bat the 2nd. Meanwhile, Nago plans to resign due to his injury, but Megumi demands he continues to fight, with her acting as his eyes.

With Wataru as the self-proclaimed King of the Fangires, Taiga confronts him and claims to have killed Maya. The brothers begin to fight, but Bishop appears with his army of Fangires, so the two switch targets, with the Arms Monsters arriving to back them up. Nago, with the help of Megumi, engages Bishop at the same time, struggling with his damaged eyesight, but with Megumi’s help, he triumphs. But in defeat, he succeeds in reviving the King, forcing the brothers to team up and fight the Bat Fangire just as Wataru and Otoya did 22 years earlier. The fate of humanity and the Fangires is about to be decided!

After Natsumi Hikari has a nightmare of every Kamen Rider being defeated by a figure called Decade, she helps her grandfather Eijiro deal with unsatisfied customers. The photographer, Tsukasa Kadoya, seems to be at fault, but he simply tells Natsumi the photos are bad because he does not belong in this world. After the argument, various holes in reality open, allowing the Orphnoch, Undead, Makamou, Worms, Imagin, and Fangires to start terrorizing their world. In the bedlam, she finds a corroded belt and book, recalling it as Decade's from her dream. She gives Tsukasa the belt and book, allowing him to transform into Kamen Rider Decade by using a card from the book and inserting it into the belt.

Arriving in the World of Kuuga, Tsukasa takes the guise of a policeman and watches Kuuga destroy a pair of Grongi, Ra-Dorudo-Gu and Me-Gyarido-Gi, before reverting to his human form, Yusuke Onodera. Tsukasa later destroys Go-Baberu-Da as Decade, but is mistaken for a Grongi by Yusuke and Ai. When Yusuke and Ai arrive at the Hikari Studio to discuss this strange Grongi, Tsukasa offers Ai his help in solving the mystery behind the Grongi's female targets and the location of their lair. On the foot of Mount Hitoki, the Grongi's Lair, Tsukasa reveals he used Ai as bait to lure out the remaining Grongi, revealing their plan to revive their leader before ruining their game. While attempting to destroy the Grongi, Decade is attacked by Kuuga, who reveals he knows about Decade's mission and will stop him at all costs.

After fending off the Hoppers who disappeared into another dimensional rift, Yusuke reveals he was told of Decade by a mysterious man. When Ai and her task force go to investigate Mount Hitoki, a black mist begins to rise from within, signaling the revival of N-Gamio-Zeda. Resurrected by the dimensional chaos, he uses his miasma to convert humans into Grongi. While Yusuke saves Ai and takes her to the hospital, Tsukasa fights the Grongi alone. A dying Ai requests Yusuke to overcome his angst and fight to protect everyone's smiles, and so Kuuga and Decade work together to destroy the remaining Grongi. N-Gamio-Zeda, in a last effort, absorbs all the Grongi to power himself up, but he is ultimately overpowered by both Decade and Kuuga, who destroy him with a combo attack.

Arriving in the World of Kiva, Tsukasa and company discover that the Fangires of this world have made a truce with the humans. However, when Tsukasa finds the Lion Fangire attacking a young woman, he transforms into Decade to fight him. Wataru, the King of the Fangire Race, witnesses this and becomes Kamen Rider Kiva to fight him with the aid of his Arms Monsters, forcing Decade to assume Kamen Rider Kuuga's Mighty, Titan, and Dragon Forms to counter. Yusuke manages to stop the fight, and the Swallowtail Fangire reveals that the young woman was actually a renegade Fangire. Yusuke reveals he has promised to help Wataru because he is uncomfortable with being the King.

As Tsukasa is fighting against Kaixa in another dimension, the Beetle Fangire defeats Wataru and becomes the new Fangire king, claiming Kivat. After the new King dissolves the truce, Yusuke arrives to protect Wataru before the boy runs off. After Yusuke expresses his reasons for helping the dethroned boy, Wataru takes refuge in the Hikari Studio. After being caught up on current events, Tsukasa makes his way to Castle Doran to save Yusuke as the Beetle Fangire absorbs the Arms Monsters into himself. After destroying the Swallowtail Fangire, Decade encounters the Beetle Fangire, who assumes Kiva's DoGaBaKi Form. When their fight makes its way to Yusuke and Wataru, the boy finds his courage to overcome his Fangire impulses and declares himself the King once more.

Upon arriving in the World of Ryuki, Natsumi goes to the Atashi Journal headquarters to learn about the world's Kamen Riders from its editor, Reiko Momoi. After Natsumi's arrival at the journal's offices, Reiko is mysteriously murdered, leaving Natsumi as the culprit as she had a small fork in her hand. Natsumi is arrested under suspicion of murder, and is to be sentenced with a Kamen Rider Trial: a system where Kamen Riders fight in the Mirror World to determine the outcome of criminal cases. Natsumi calls upon Tsukasa to be her lawyer, who meets with Shinji Tatsumi to hear what he knows of what happened to Reiko. As Shinji reveals that he is Kamen Rider Ryuki and he believes Natsumi was framed, his former friend Kamen Rider Knight is fighting in the Kamen Rider Trial, defeating several opponents. Shinji suggests to Tsukasa that he should fight as Decade in the Kamen Rider Trial to clear Natsumi's name.

After defeating Knight, Decade is about to finish him off when Ryuki pleads with him not to deliver the final blow, as he feels Knight must answer for his crime by his hand. However, Abyss uses this time to make his move to take out all three Riders at once, forcing them to retreat with Ren refusing to answer Shinji as he leaves. After her brief encounter with Narutaki, Natsumi learns that Shinji and Tsukasa are convinced that Ren is Reiko's murderer, although Yusuke sees otherwise. Meanwhile, a wounded Ren battles Kamen Rider Odin and defeats him, emerging from Mirror World with Odin's Time Vent as Shinji and Yusuke find him. Learning that Ren obtained the card to save Reiko, Shinji uses the card to go back in time as Tsukasa holds Abyss off. Arriving seconds before Reiko's death, Shinji and Tsukasa manage to save Reiko with the latter cornering her true murderer, Kamata.

Arriving in the World of Blade, Tsukasa assumes the disguise of the Chief Waiter of the BOARD Corporation, an organization whose agents become Kamen Riders to battle the Undead. When the Elephant Undead goes on the attack, Sakuya Hishigata battles the Undead as Kamen Rider Garren as Kazuma Kendate arrives and transforms into Kamen Rider Blade. When the Capricorn Undead joins the fray, Tsukasa joins the fight, dispatching the Elephant Undead using Ryuki's powers. Afterwards, Natsumi and Yusuke meet BOARD's president Hajime Shijo, who decides to promote Tsukasa to the rank of King while Kazuma Kendate is demoted from Ace to 7 and Mutsuki Kuroba is promoted from King to Ace, thereby becoming Kamen Rider Leangle.

Decade continues his fight with Chalice, with Garren losing his Garren Buckle in the process. The fight comes to a sudden halt when Kamen Rider Todoroki shows up. Back at BOARD, Hishigata is demoted to Rank 3 while Kazuma is fired from BOARD. After he understands Tsukasa's intent to help him, Kazuma stays on in the kitchen as he opens the Ace Lunch to all BOARD members. Meanwhile, Mutsuki and Hishigata search for Chalice to get back the Rider systems, and are subsequently ambushed by Chalice, who knocks them out after they find out his true identity. After hearing that the two have supposedly resigned from the company, Kazuma decides to find Hajime with Yusuke's help.

Upon arriving in the World of Faiz and once more encountering the mysterious Daiki Kaito, Tsukasa finds himself in a school uniform and enrolled at Smart Brain High School. He learns that the high school is attacked on a nightly basis by beings called the Orphnoch, with only Faiz to protect the school. Daiki challenges Tsukasa to find out who Faiz is, and Tsukasa then challenges the Lucky Clover clique to a tennis match to see if any of them are Faiz. He beats them, learning that they are Orphnoch who are also after Faiz, and is forced to become Decade, using Blade's power against them. However, Decade is outclassed when Momose appears as the Tiger Orphnoch and warns him to back off.

After Tsukasa recovers the Faiz Gear, he learns Diend's reasons for wanting the belt before Takumi regains it so he and a shocked Yuri can escape on the Autovajin. However, as he exposed himself as the Wolf Orphnoch to protect her only to be forsaken, a saddened Takumi attempts to dispose of the Faiz Gear into the river. Managing to save the Gear while following him, Tsukasa returns to the photo studio where he put Yuri's confusion at ease. The next day, Daiki attacks Takumi to get the belt from him, nearly killing him when Tsukasa arrives with it. Refusing to take Tsukasa's words of something more precious than the Faiz Gear seriously, Daiki takes Decade's Ride Booker, and Narutaki takes advantage of the situation as he takes Tsukasa into another dimension to be killed by Kamen Rider Ryuga.

Upon arriving in the World of Agito, Yusuke is shocked that there are Grongi in the world which are being dealt with by Kamen Rider G3-X. He is further shocked when he sees an interview with Toko Yashiro, who is physically identical to the Ai Yashiro that died back in the World of Kuuga. Arriving at the police station, Yusuke offers to be the new user of the G3-X suit, but loses the position to Kaito. While this occurs, finding himself in a mailman outfit with a letter to Shouichi Ashikawa, Tsukasa and Natsumi find the man before they are attacked by what they think to be a Grongi. But during the fight, Tsukasa realizes he is fighting an Unknown, an Ant Lord called Formica Pedes.

After Yusuke saves Tsukasa from Delta's attack, Gills is about to fight when he's overcome with pain as the Unknown shows up to kill him. As Shouichi escapes, Toko recognizes him via G3-X's camera. While Tsukasa insists on protecting an annoyed Shouichi, Yusuke reports the defeat of the Grongi and the emergence of the Unknown. He finds Toko saddened, but has little time to help her as Kaito takes the G4 chip stored within his locker. Yusuke demands the chip back, but during the struggle, Toko blasts the chip to bits and a disappointed Kaito leaves. The next day, as Tsukasa continues to keep Shouichi safe from the Unknowns' attack, Yusuke learns that Shoichi was the original user of the G3 suit when he receives the letter for Shouichi from Toko.

When the Hikari Studio appears in the World of Den-O, Tsukasa finds himself dressed in a strange detective-like attire with possession of a Rider Pass. He is then suddenly possessed by an Imagin, who battles a Mole Imagin as Kamen Rider Den-O. After taking out the Imagin, the possessed Tsukasa walks off until Natsumi uses her pressure point move to drive the Imagin out of him. When the Imagin known as Momotaros tries to possess Tsukasa, again, he throws Yusuke in front of him and Yusuke becomes possessed. After easily overcoming M-Yusuke and treating him to pudding for answers, Tsukasa learns that the Imagin lost his physical form some time before they arrived.

After getting on the DenLiner, Tsukasa takes pictures of the DenLiner's gang before the Taros. But after Kohana sets the three Imagin in their place, they suddenty find the Hikari Studio as the front car. Kohana explains to Natsumi about the Imagin's new attack pattern as well as Momotaros, who Tsukasa decides to find. After surviving his confrontation with Diend and taking out another Mole Imagin, M-Yusuke tends to his injuries as Tsukasa finds him and scolds him for being an idiot. M-Yusuke senses the Imagin boss, and he and Tsukasa chase after the Alligator Imagin until he reveals himself. Using the Mole Imagin to cover his escape into the past, the Alligator Imagin battles Den-O and Decade, using the former's own DenGasher against him.

After helping the DenLiner gang in the past, Tsukasa and company begin their venture in the World of Kabuto. Posing as a ZECT Trooper, Tsukasa is deployed to aid Bright Troopers in the containment of a Worm as Kamen Riders Gatack and TheBee manage to exterminate it with the unseen aid of Kabuto. Soon after, Tsukasa brings Arata to the Studio to explain about his world, only to find a Worm had mimicked Tsukasa's form. After Natsumi uses the pressure point to expose one of the Tsukasas as a Worm, Decade fights it before it attacks a girl and is destroyed by Kabuto. Deciding to investigate the girl Mayu, they host a photo shoot for her, and Natsumi learns of Mayu's older brother who was supposedly killed by Kabuto. At ZECT's headquarters, TheBee's user, Sou Otogiri, tells Arata that the final prepation for the plans to capture Kabuto are nearly done.

Believing that TheBee's user is her brother, Mayu attempts to look for him with Natsumi's aid until they are attacked by a Worm. Counting on Kabuto to save them, Diend fights him to acquire his Clock Up system, summoning Ixa and Psyga to hold him down before Kabuto defeats them and runs off. By the time Tsukasa finds Natsumi and Mayu, the latter is shocked that she became a Worm as she runs off. She runs into Sou who reveals himself as the Phylloxera Worm and brings her to ZECT HQ as part of the Kabuto Capture plan, much to Arata's dismay before he is beaten to a bloody pulp questioning the plan. After escaping, Arata makes his way to Tsukasa and reveals the plan to him, confirming Tsukasa's notion. Kabuto falls for the trap as the Clock Down takes effect while the Worms reveal themselves among the ZECTroopers, with Sou exposing Kabuto as Mayu's real brother Souji.

Arriving in the last world, the World of Hibiki, Tsukasa and company begin the search for Kamen Rider Hibiki when they are ambushed by the Makamou Kappa. An Oni in training named Asumu battles the monster until Decade uses Kabuto's powers to destroy it. On learning he is Hibiki's pupil, Tsukasa has Asumu bring him to his mentor. Upon seeing Tsukasa, Hibiki, who is shirking off from his duties as an Oni, believes him to be the legendary Ongekidō Grand Master. Meanwhile, Zanki slays a band of Bakeneko as Ibuki arrives to take them out as well. But when the last Bakeneko escapes them, Decade destroys it with the two groups as witness. Tsukasa visits Ibuki's school afterwards and talks with Ibuki and Akira about three special scrolls. Meanwhile, after failing to rob Hibiki as he takes his leave, Daiki is forced into becoming Asumu's mentor.

Using Ryuki's powers, Decade battles Gyuki while Ibuki and Zanki argue whose fault this was. When Akira and Todoroki join the fray in their Oni forms to save Asumu as he tries to protect them, with Decade joining them by using Den-O's Ax Form, they manage to defeat Gyuki. He runs off before regressing to Hibiki, and Yusuke and Natsumi find him shortly after. Later that night, after talking to Asumu, Akira and Todoroki confront their mentors to put aside their differences, with Tsukasa supporting them. Ibuki and Zanki promote them to the role of new teachers of their respective schools. Meanwhile, Hibiki reveals the nature of Gyuki to Yusuke and Natsumi as Daiki arrives to claim the last scroll.

With their tour of the nine Kamen Rider Worlds complete, the Hikari Studio group returns to their home world, finding it as it was before the monsters appeared. Tsukasa is the only one who feels something is not right and questions the reason for the journey. Before Yusuke or Natsumi can attempt to answer, they encounter the violinist Otoya Kurenai, who thanks them for saving the world and tells Tsukasa that he earned a world of his own for his journey. As Natsumi goes out to see her TG Club friends and teacher for a high school reunion, Tsukasa and Yusuke have a short encounter with Narutaki who congratulates him on getting his own world.

After Tsukasa suddenly loses his powers, he learns from Kaito that he is actually in the World of Negatives. He later is seen by a talent agent and is offered to be signed onto his agency to become an idol. Although Yusuke acts as the voice of reason, he gets caught up in the fame seeking as well. Meanwhile, after her school friends return while waiting for Chinatsu, Natsumi that suggests that they should dig up the "treasure" they buried together, only to find that a parking lot was built over it and learning that Chinatsu moved their treasure prior. Once, Tsukasa finds Natsumi, he attempts to tell her that they are not in the real world, but Natsumi refuses to accept this as she runs off to the TG Club's hideout where she also meets the World of Negatives's Natsumi.

Arriving in Kaito's homeworld, the World of Diend, Tsukasa finds the world in peace and harmony, but with Kaito a wanted man. As Tsukasa assumes the role of a traveling salesman, he meets Kamen Riders Larc & Lance as they battle a Darkroach. After destroying the monster, Tsukasa learns that the world's residents kill Kamen Riders. As Tsukasa and company meet the head of area management committee, Junichi Kaito, Larc and Lance battle the Darkroaches until they receive aid from Diend. Saving them from reinforcements, Tsukasa learns from Haruka and Shin that the world is ruled by the mysterious Fourteen who uses his Roaches to manipulate humans.

Nearly killed by Lance, Kaito is spared when Larc stops her partner as he reminds her that he is the reason that Junichi is under Fourteen's control. After escaping the angry mob, parting from Haruka and Shin, Kaito and Tsukasa find Natsumi who tells them that Yusuke has been kidnapped by the Roaches before Junichi arrives. After remembering the events leading to his brother's enslavement, Kaito is reluctant to fight as he and Tsukasa transform to follow Junichi, leaving the brain-washed Yusuke behind and taking Natsumi to undergo the process as well.

Arriving in the new world with a strange card in hand, Tsukasa finds himself in the costume of a kuroko before running into Daiki who just stole a squid-like artifact. Daiki mentions that this world is not like the other A.R. Worlds before running off prior to the appearance of mysterious red fish-like monsters. Tsukasa is about to transform before several other Kuroko show up along with five young men and women who transform into the Shinkengers to fight drive them back into the Sanzu River.

After Tsukasa reveals himself, Takeru realizes that Tsukasa is the "Decade" Narutaki warned him about. Before the two can fight, Narutaki arrives to tell Tsukasa he is to blame for the terror brought unto the world by the Ayakashi Chinomanako who now has the powers of Diend, and that the only way to save the worlds he entered if he ceases to exist. After Takeru takes out the Nanashi and drives off Chinomanako as Shinken Red, Genta attacks Tsukasa believing that he is in league with Daiki until Natsumi takes him to the Hikari Studio, where Hikoma Kusakabe is hiding.

Tsukasa finds himself wearing strange clothes with another strange card as he, Natsumi, and Yusuke find themselves attacked by the Strange Demon Robot Schwarian and his Chaps as Kamen Rider Black RX battles them, with both sides believing Tsukasa to be Joe the Haze. When the Seamoon Fangire and Scorpion Imagin suddenly appear, Tsukasa becomes Decade to help RX out against the monsters with Agito's power as Schwarian runs off. After Natsumi stops RX from attacking Decade, RX takes her words to heart and sees Tsukasa as an ally.

Following Apollo Geist into another A.R. World, Decade is attacked by Kamen Rider Black until Diend arrives and summons Femme to hold him off. The next day, after learning that he is in the World of Black and seeing that he is on his own in saving Natsumi, Decade ambushes Guy as Ryuki and fights him until he uses a little girl as his hostage. When Decade takes a hit from Diend to save the child, Black watches and has second thoughts about him as Apollo Geist escapes.

Arriving in a new A.R. World, finding himself in a baseball uniform, Tsukasa notices the people are acting strange while saluting each other before he, Natsumi and Yusuke are singled out as rebels against Dai-Shocker with Propheta Cruentis, Go-Jaraji-Da, and Camponotus Worm Maxilla appearing to exterminate them. Amazon arrives to their aid, fighting the monsters with Decade backing him up as the people back up the surviving monsters under a boy named Masahiko.

Evading Apollo Geist and Llumu Qhimil with Diend's attempt to get the GaGa Armlet, Tsukasa has his wounds tended to by Natsumi in Dai-Shocker's school before Yusuke and a weakened Amazon join them, revealing that Masahiko took the GiGi Armlet as Ritsuko arrives and calls in the Dai-Shocker Soldiers after them despite Tsukasa questioning her faith in Dai-Shocker. Later after finding the Hikari Photo Studios in ruins, Amazon ponders if he should join them.

When Natsumi realizes that this is the world from her nightmares, she becomes wary for Tsukasa's well-being. Finding him in a tuxedo and feeling that this is the final chapter to their journey, they witness Wataru and Kazuma leading their respective Rider/monster groups against each other. After Rising Ixa and Leangle are killed off in the fight, Tsukasa makes his way to Wataru as he grieves over Ixa's death. Meeting the Fangire Queen Yuki, they learn from Wataru that the Riders are fighting each other to maintain the existence of their worlds.

After fighting off the Riders, Super Apollo Geist takes Natsumi to be his new bride as he flees. Kazuma Kenzaki appears, saying that Tsukasa's existence is the real cause of the worlds blending before confronting him as Kamen Rider Blade in King Form in order to force him to leave the world at once with Asumu keeping Yusuke and Wataru from interfering as Decade is easily defeated.