Tetsudo Hisakawa, commonly called Poppo, serves as a core member of the childhood friend group known as the Super Peace Busters. As a child, he sported a shaved head and simple attire like a blue hoodie and track pants. As a teenager, he grows significantly taller, reaching 183 cm, with mid-length brown hair and brown eyes. His typical outfit features a lilac bandana, layered shirts, olive pants with a blue pearl necklace attached, sandals, and a distinctive pouch necklace containing flowers blooming near the site where Meiko Honma died. Poppo displays a cheerful, easygoing, and optimistic demeanor in the present timeline. He funds his travels through various part-time jobs, having dropped out of school, and lives in the group's childhood secret base when not abroad. His initial belief in Jinta Yadomi's ability to see Meiko's ghost helps facilitate the group's reunion. Poppo frequently acts as a mediator during conflicts, showing empathy and a desire to maintain harmony. However, this outward positivity masks deep-seated guilt over his perceived failure to prevent Meiko's accident. His emotional vulnerability surfaces when confronting repressed memories of her death. Poppo's childhood involved admiration for the group's leader, Jinta, and gratitude for being included despite social awkwardness. After Meiko's death, he coped by distancing himself through travel, yet remained emotionally anchored to the group. His character arc centers on acknowledging his guilt and participating in fulfilling Meiko's final wish, leading to catharsis and a shift from avoidance to acceptance. In post-series continuity, Poppo demonstrates emotional recovery. He no longer feels tormented by guilt and maintains connections with the Super Peace Busters. The group collectively writes letters to Meiko annually. Poppo later marries and has children, distinguishing him as the only group member to start a family.