Shūji Fujimoto is a student at Shiratake High School and the charismatic leader of the Fujimoto Corps, a delinquent gang. He initially exhibits hostile behavior towards the main protagonist, Ikedo Sadaharu, tripping him during Ikedo's transfer. Fujimoto embodies the sociable yanki leader archetype, central to early conflicts and romantic subplots. His gang begins as bullies targeting Ikedo, but their relationship evolves into camaraderie marked by lighthearted jest.

In the original series' final arc, Fujimoto faces coercion from a member of Ikedo's family business, forced to sell overpriced stickers under threat of violence. He submits to the pressure, demonstrating a lack of courage under duress. This contrasts with Ikedo's defiant response, positioning Fujimoto in a supporting role during the conflict. He achieves only a minor victory in a side fight before the climactic showdown, highlighting the contrast with Ikedo's resolve.

Decades later in the sequel "Gorillaman 40," Fujimoto reappears as an adult. He retains his sense of justice, intervening against thugs illegally occupying disabled parking spaces and harassing families and the elderly. This confrontation results in his assault, prompting Ikedo's return. Fujimoto is now a family man, father to a daughter named Mayu, who participates in her high school's dance club. He attends the school's cultural festival, recording Mayu's performance on his cellphone, and engages normally with Ikedo and their old associate Fujise Kenji. His characterization emphasizes his transition into a responsible, conventional father figure while maintaining his foundational moral compass and past friendships.