Bianchi takes Kyoko and Haru to the Vongola base while leaving Tsuna and his guardians to discuss the upcoming battles with Shoichi. Byakuran sends a holographic image stating he wants to have an official battle between the Vongola and the Milliefiore in a battle of Choice. He reveals to Irie that the Funeral Wreaths and the mare rings they wielded were fakes and he had gathered the Real Six Funeral Wreaths in secret from Irie as he had expected the betrayal. Byakuran then activates the teleportation system in the Merone base transporting all but the White Round Machine, and Tsuna along with his friends. Irie reveals that since they have completed the Arcobaleno trials, Tsuna's guardians are given their respective Vongola boxes for the upcoming battle.

After a long discussion, it is decided Tsuna and his friends rest for the first few days before commencing training for the battle of Choice in ten days time. At the Vongola base, a ring signature was caught on radar and Tsuna and his friends investigate. Tsuna and his friends find Basil from ten years ago to be the cause. At the Vongola base, Basil explains he was sent to the future ten days ago and was given a ring, a box weapon, and a book containing information about his situation and orders to assist Tsuna and his friends.

Tsuna and his friends split up and explore the Namimori of the future. They all coincidentally meet in front of their school, Namimori Middle, and relax in their classroom. Tsuna realizes that to return to their own time, they must defeat Byakuran in the battle of choice. On the roof of Namimori Middle, Hibari encounters the future Dino who insists on training him.

Kyoko and Haru become concerned that Chrome has not been eating, since she is not used to the kindness of others. Hoping to cheer her up, Tsuna attempts to find out more information on Mukuro's whereabouts from Irie, but to no avail. During a welcome party for Basil, I-pin sneaks off into Chrome's room and manages to get her to eat some gyoza. The next day, Kyoko and Haru find Chrome helping out with the dishes, and they start to become good friends.

Gokudera brings a newspaper from the current time from which Yamamoto learns about Namimori Middle's baseball team's consecutive losing streak and how the baseball club may be canceled. He heads to Namimori middle and runs into three first year members of the baseball club and offers to train them for the upcoming game. The next day, Tsuna and his friends watch the game. Namimori middle baseball team becomes discouraged as the mercy rule will be imposed if they can not gain a point. The batter, being one of the three trained by Yamamoto, remembers he should do his best for friends, and hits a home run. Yamamoto feeling satisfied with the team's progress, promises to help Tsuna defeat Byakuran.

Reborn tells Tsuna and his friends that they must master the airbikes before the Battle of Choice. While Tsuna's friends have quickly mastered the airbikes, Tsuna has yet to grasp the basic. While talking to Kyoko and Haru, Tsuna realizes he must learn how to ride the airbike one step at a time and continue to practice. With the help of his friends, Tsuna is able to grasp how to ride the airbike.

After they finished practicing on the airbikes, Reborn tells Tsuna and his friends they shall train tomorrow on opening their respective Vongola Boxes. Tsuna's box weapon shakes violently that evening and Tsuna opens it and releases his box weapon. Tsuna's box weapon attacks him and with the help of Yamamoto and Basil, they are able to seal the box weapon back to its box. Dino arrives and tells Tsuna his box weapon attacked him because he opened it incorrectly and comments that the Sky Box Weapons must be used delicately.

Dino in his room unleashes his box weapon but is accidentally swallowed by it. One by one, Tsuna's friends are swallowed by the box weapon until Tsuna and Basil are the only ones who remain. Tsuna contemplates to destroy the box weapon to stop the menace but hesitates when he realizes his friends will die with it. The box weapon begins to lay eggs and inside are Tsuna's friends who has been eaten by the box weapon. Dino reveals that the box weapon he bought rejuvenates those that it eats. Reborn tells Tsuna and his friends that they will begin to train with their Vongola Boxes.

Dino gives each of the Vongola guardians individual training regimes for their Vongola Boxes. Unbeknownst to them however, Haru and Kyoko had eavesdropped on their conversation. Lambo manages to open his Vongola Box, but Tsuna still has trouble controlling his. Meanwhile, Squalo travels to Japan.

Kyoko and Haru confront Tsuna and company about what they heard. When Tsuna refuses to tell them anything, the girls start a boycott, refusing to do any housework until they tell them. The guys struggle to do the housework, as well as their training. After talking with Bianchi and noticing Chrome's training wounds, the girls reconsider their decision. Tsuna is tricked by Bianchi into thinking Kyoko is in danger and rushes after her. Although Kyoko decides to end the boycott, Tsuna decides to tell her everything anyway, having realised how selfish he was being. After talking with Kyoko, she helps Tsuna figure out how his Vongola Box works.

Tsuna tells everything he told Kyoko to Haru, who is a bit shocked at the scale of everything, but holds in her sadness until Tsuna leaves. Byakuran hacks into the communications system, giving them the date and location of Choice, and informing them that they will need to bring everyone who came from the past, including Kyoko and Haru. Reborn lets slip that Tsuna told the girls everything, which makes Ryohei mad at Tsuna, even punching him. Just then Squalo appears, beats up Yamamoto and takes him away in order to train him. During the six days leading up to Choice, everyone manages to finish their training.

As the Real Six Funeral Wreaths prepare for battle, Tsuna pays a visit to Lal Mirch. Afterwards, everyone puts on special mafia suits made from Leon's thread. They arrive at Namamori Shrine, where Shoichi has prepared a base of operations. However, Yamamoto and Hibari have yet to arrive. Byakuran appears, telling them they'll need to provide a massive amount of Dying Will flame energy to activate a teleporter to take them to the battlefield. Yamamoto and Hibari arrive at the last minute and, with their Vongola Boxes, the group manage to produce double the power needed.

Tsuna and co are transported to the center of an abandoned city where the battle of choice is to take place. They spin a roulette to decide which members will participate in the battle. Tsuna's team consists of Yamamoto, Gokudera, Irie, Spanner, and himself while Byakuran's consists of Kikyo, Daisy, Torikabuto, and Torikabuto's underling Saru. Before the battle begins, Byakuran explains that each team has a target that must be defeated in order to win the battle; the target for the Millefiore family is Daisy while the Vongola's is Irie. The winner of the battle shall be awarded the Mare Rings, Vongola Rings, and Arcobaleno Pacifiers.

After setting up their base, Shoichi guides Tsuna through the intercom where he runs into Torikabuto. Tsuna is seemingly overwhelmed by Torikabuto's attacks until he releases his box weapon, the Sky Lion Na-Tsu. Torikabuto surrounds Tsuna with projectile attacks and seemingly impales him in a sphere of needles. However, Tsuna transforms Na-Tsu into a cloak and wards off the attack.

After Tsuna defeats Torikabuto with the help of Na-Tsu, Yamamoto encounters Saru. Saru reveals himself to be none other than Genkishi. However, Yamamoto surprises Genkishi with Kojiro, his box weapon, merging with Shigure Kintoki to form Asari Ugetsu. His other box weapon, Jiro, changes his three small swords as well.

Yamamoto defeats Genkishi and incapacitates him. While Genkishi expresses his disappointment not being one of the Real Six Funeral Wraths and not being appointed Byakuran's most trusted soldiers, Kikyo uses his box weapon and kills Genkishi. Kikyo reveals to Genkishi that it was under Byakuran's order to kill him when his usefulness is fulfilled. Tsuna's friends realizing, Byakuran's true nature, become even more motivated to win the battle of Choice.

Kikyo reveals that the Funeral Wraths were holding back to entertain Byakuran who has become tired of flawless victories. Kikyo is able to bypass Gokudera and approaches the base where Irie is currently hiding. At the same time, Yamamoto attempts to break through the barrier and defeat Daisy before Irie is killed. Tsuna meanwhile is trapped in an illusion by Torikabuto who was revealed to have faked his own defeat.

Irie mobilizes the base in an attempt to escape from Kikyo. After a long chase scene, Kikyo manages to destroy the base and inflicts a fatal wound on Irie. At the same time Yamamoto breaks through the barrier and defeats Daisy and extinguish his marker. Tsuna, having escaped from Torikabuto's illusion with the use of his X-Burner, arrives to finds the marker on Irie has been extinguished. Daisy however regains consciousness and is able to relight his marker causing the Millifiore to be pronounced the Winner of Choice.

As Irie recovers from his injuries, he explains to Tsuna and the others about why is he obsessed with Byakuran. Using Ten-Year-Bazooka ammo he had received from Lambo's family 11 years ago, Irie went to the future and ran into Byakuran. When he revisited it, hoping to change, it awakened Byakuran's ability to retain the knowledge of different parallel worlds. Byakuran used this knowledge to conquer and destroy several parallel worlds. Eventually, the future Irie arranged for the younger Irie's memories to be temporarily wiped for five years in order to gain Byakuran's trust, since the current world is the only one that is not ruled by Byakuran.

Irie reveals that their world has not been taken over due to his and Future Tsuna's intervention and that the plan to bring their past selves to the future was thought of by Future Tsuna. Byakuran demands the surrender of the Vongola rings after the Choice battle. However, due to Byakuran owing Irie a favor and Yuni's, the second leader of the Millifiore Family, opposition, the match is annulled. Yuni asks Tsuna to protect her and announces to Byakuran she will be defecting from the Millifiore.

Tsuna and co. manage to ellude Byakuran with the help of an illusion made by Mukuro Rokudo and manage to activate the transport device returning them to Nanimori. While sheltering at the Vongola base, Tsuna wonders if they can defeat Byakuran.

After Tsuna and his friends escape from Byakuran with the help of Mukuro Rokudo, Reborn visits Lal and updates her on the events happened so far about choice. As Lal hears every word, Reborn states now its up to them to protect Yuni from Byakuran and protect the future.