Kinji Ninomiya's life is all set up. He has a stable income and a great apartment, allowing him to live the rest of his life without doing any work at all. His dreams have come true - until a mysterious portal transfers him to a foreign world.

Though Kinji's plan to make easy money ultimately failed, the revenue he generated during his temporary success was noticed by his superiors. Kinji and Wanibe are transferred to a more dangerous division, to do a job they are totally unqualified for.

Kinji's next plan is to put his new allies to good use by transferring to a different group within the company with more free time. However, before he can do that, he must first endure a deadly corporate training trip.

Shia is determined to continue being a loyal corporate soldier, despite Kinji's best efforts. However, the company, and the dungeon it manages, seems to have a much more complex plan for her.

Several high-ranking members of the Demon Lord's Army are threatened by Kinji's meteoric rise, and decide to take action against him. Meanwhile, Ranga is haunted by a secret from his past.

Kinji meets the Demon Lord and learns the truth behind this world, its problems, and how he ended up getting involved. He is given a choice - save the world, or return to his home in Japan.

During Kinji's absence, the dungeons have become more dangerous. In order to access the ruins inside, Kinji must find a way to push through the dungeons quickly, but it becomes quickly apparent that no amount of training will help.

After being stripped naked by his magic gun, Kinji and his party must find a way to acquire replacement gear. However, the adventurer's fortress inside the dungeon is suspiciously empty.

Kinji reaches the fourth "floor" of the dungeon - a lush forest environment with a sky, geography, and a thriving ecosystem. He must find a way to unblock the path to the fifth floor.

Belza's Bodyguards have been all but totally defeated by the fierce Guardians of the fifth floor. In the nick of time, a hero arrives to save them - Kinji Ninomiya.

Belza strikes back against Kinji by gathering evidence to report Kinji to the authorities. Kinji is placed under arrest for numerous serious charges, some of which are actually true.