Kazuki asks for Toi's help to kidnap Sara and so that he can take her place during a meet-and-greet that Haruka plans to attend. Toi's backstory is revealed through a flashback – after his parents died from suicide upon being conned into crippling debt, the family's soba shop was saved from closure through Chikai's intervention. When a yakuza came to collect the family's debt, he was shot by Toi, which was subsequently covered up by Chikai.

Toi attempts to kidnap Sara, though she evades him by transforming into a kappa, exposing Kazuki's crossdressing to his family. Kazuki reveals that he is adopted, and that he blames himself for Haruka's disability when he was hit by a car after they had a fight. Kazuki's turmoil causes him to fail in defeating the episode's zombie; an angry Keppi subsequently refuses to transform the group back into their human forms.

The group rescue Haruka after he is kidnapped by Reo, and are transformed back into human form. Keppi explains that Reo and Mabu are agents of the Otter Empire, who have been at war with the Kappa Kingdom for generations over the energy of the shirikodama; with the Kappa Kingdom now defeated, the Otter Empire has begun to extract the shirikodama of humans. In a post-credits flashback set during the Otter-Kappa war, Mabu sacrifices himself to protect Reo in battle.

In a flashback, Mabu is brought back to life with a mechanical heart transplanted by Otter, though Reo believes that Mabu is merely a re-animated facsimile. Chikai's criminal dealings force him to flee the city, and Toi announces that he intends to join his brother. The group agrees to use the dishes to help Chikai, but discover they have been stolen. Upon defeating a kappa zombie, Enta is exposed as having stolen the dishes out of jealously over Kazuki's concern for Toi.

Chikai and Toi make preparations to leave the city. Enta returns the Dishes of Hope to Kazuki, but they are confronted by Reo and Mabu, who intend to use the dishes to restore Mabu. Reo shoots Enta, and takes the dishes.

Keppi transforms a hospitalized Enta into a kappa so that he and Kazuki can recover the dishes. Reo witnesses Otter performing sexually-charged "maintenance" on Mabu's heart; when he intervenes, Otter appears in the form of Reo, and explains that he is a mirror of Reo's inner desires. Meanwhile, Chikai is shot and killed in a confrontation with the yakuza.

Toi begins to destroy his connection to Kazuki and Enta, but ultimately chooses to preserve it. Keppi fuses with Dark Keppi, with assistance from the group and a revived Reo and Mabu, and defeats Otter and the concepts it represents. Upon performing sarazanmai, Kazuki, Toi, and Enta foresee a potential future in which their connections to each other are eventually severed. In the aftermath, Toi is sent to juvenile detention for three years. Upon his release, he jumps off of the Azuma Bridge, but is rescued by Kazuki and Enta. The three happily run "off to the future" together.