After accidentally breaking a statue of a kappa at a shrine in Asakusa, middle school student Kazuki Yasaka encounters Keppi, heir to the throne of the Kappa Kingdom. He, along with his classmates Toi Kuji and Enta Jinnai, enrage Keppi by calling him a frog; he steals their shirikodama, a mythical organ located in the anus that stores an individual's desires, and transforms them into kappas. Keppi informs them they must defeat a zombie by extracting its shirikodama in order to become human again. They are successful, but the act of "Sarazanmai" to transfer the shirikodama to Keppi exposes Kazuki's secret to the group: that he cross-dresses as the idol Sara Azuma. In a post-credits scene, police officers Reo Niiboshi and Mabu Akutsu extract the desires of a man they are questioning.

Keppi gives the group a Dish of Hope as thanks for helping him, which grants one wish to whomever possesses it, and informs them that they can earn more plates by defeating more zombies. Kazuki explains that he cross-dresses for his younger brother Haruka, a fan of Sara's, and that he wishes to earn a dish for him. Toi wishes to earn a dish for his older brother Chikai, a yakuza for whom he sells cannabis. Kazuki and Toi are later forced to pursue Nyantaro, a feral cat cared for by Kazuki and Haruka, after he steals a bag of cannabis from Toi's grow-op. Nyantaro is suddenly captured by a kappa zombie who, upon being defeated, exposes Kazuki's secret that Nyantaro is domestic cat that he stole. In a post-credits scene, Enta encounters a sleeping Kazuki dressed as Sara, and kisses him.

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.