"Hitorijime My Hero" is a manga series that blends romance, drama, and slice-of-life elements, centering on the lives of its main characters and their evolving relationships. The narrative primarily revolves around Masahiro Setagawa, a high school student who has long been entangled with a local gang, and Kousuke Ooshiba, a math teacher who becomes a protective figure in Masahiro's life. Kousuke, known as the "Bear Killer" for his past as a gang leader, takes Masahiro under his wing, offering guidance and support as the younger boy navigates his troubled circumstances.

Masahiro's life takes a turn when he begins to develop feelings for Kousuke, who reciprocates his affection. Their relationship evolves from a mentor-student dynamic into a romantic one, though it is complicated by societal expectations and the challenges of their age difference. Alongside their story, the manga explores the relationship between Masahiro's childhood friend, Kensuke Ooshiba, and Asaya Hasekura, a classmate who harbors feelings for Kensuke. Kensuke, Kousuke's younger brother, initially struggles with his own identity and feelings, but his bond with Asaya grows into a heartfelt romance, adding depth to the narrative.

The series delves into themes of love, self-discovery, and the complexities of human connections. It portrays the characters' struggles with personal growth, societal pressures, and the pursuit of happiness. The interactions between the main characters are central to the story, with their relationships serving as the driving force behind the plot. The manga balances moments of lightheartedness with emotional depth, creating a narrative that resonates with readers through its exploration of love in various forms.