Chitan Tsubouchi, the smallest member of the Science Club, is immediately identifiable by his thick glasses. He acts as a personal punching bag for others and habitually assumes the role of an underling for Kaizō Katsu, a position often symbolized by his wearing of various underling suits. A dedicated rail enthusiast, he frequently carries a model train and exhibits a profound interest in trains. Despite this primary obsession, he displays a natural and extraordinary talent for soccer, regarded by others as a god of the sport, though he himself shows no inclination to develop this ability.

He has a twin brother, Satan Tsubouchi, who is his physical and personality opposite. While Chitan is small and bespectacled, Satan begins with an identical appearance but a different skin tone, and over time grows taller and more conventionally attractive. Conversely, Chitan becomes progressively shorter and less attractive. Chitan works a part-time job where he develops a romantic interest in his junior coworker, Arumi Haku. This infatuation leads him to stalk her, though Arumi remains unaware he is the stalker and instead confides in him about her distress.

In the conclusion, the entire world and its characters are revealed to be an elaborate fantasy constructed by Kaizō and Umi, patients in a mental ward, where Suzu Saien is their doctor. As a result, Chitan Tsubouchi, like all characters except Kaizō and Umi, is not real but a figment of their shared imagination—a model within a constructed city used for therapy.