Tetsudo "Poppo" Hisakawa served as the youngest member and little brother figure within the core childhood friend group, the Super Peace Busters. After the accidental death of their friend Meiko "Menma" Honma fractured the group, Poppo diverged from his peers' educational paths, becoming a high school dropout who traveled the world taking odd jobs. Between journeys, he resided at the group's former childhood hideout, maintaining a tangible link to their shared past. Outwardly, Poppo consistently displays an easygoing, upbeat, and optimistic demeanor, making him the most fun-loving member. Though maintaining this cheerful, happy-go-lucky personality, he privately carried unresolved trauma directly tied to Menma's death, as he was the sole witness to her drowning. This secret burden profoundly impacted him, initially concealed behind his bright facade. Poppo played a pivotal role in reuniting the estranged friends when Menma's ghost appeared to Jinta. He was the first to wholeheartedly believe Jinta's claim of seeing her spirit, influenced by his secret knowledge of the accident. He actively participated in and often facilitated the group's efforts to uncover and fulfill Menma's final wish, demonstrating deep loyalty and high regard for his former friends, particularly Jinta. As an adult, Poppo achieved significant stability. He co-founded an import business with Jinta, channeling his global travel experiences into a legitimate enterprise. He also established a family, marking his transition from a transient lifestyle to a settled, responsible existence, signifying his navigation through past trauma toward personal fulfillment and enduring friendship.