Genzou is a resident of Cocoyashi Village in the East Blue, where he serves as the local sheriff and is regarded as the village leader. He is a middle-aged man with a tough, intimidating appearance, marked by visible scars that are stitched across his body. Despite his stern look, he is deeply kind-hearted, caring, and protective, especially toward the villagers he has sworn to guard. His most recognizable feature is the small pinwheel he wore on his hat for many years, a tradition he started after discovering that the spinning toy made a baby Nami laugh instead of crying when she saw his frightening face. This pinwheel became his personal symbol, representing his bond with the girl he would come to see as a daughter.

Genzou has a long history with Cocoyashi Village, having grown up alongside Bellemère, Nami and Nojiko’s adoptive mother. He knew Bellemère as a troublemaker, and though he was initially shocked when she decided to adopt the two girls, he remained closely involved in their lives. Acting as a father figure to Nami and Nojiko, he watched over them constantly, especially concerned about Bellemère’s ability to raise them, and eventually simply wished to see them live together as a happy family. His protective instincts are central to his personality. When the Arlong Pirates took over the island, he tried to stop them and was brutally attacked, receiving the severe scars he still carries. He witnessed Bellemère’s death and was powerless when Arlong took Nami away to force her into service as a cartographer. Despite his anger when Nami seemingly joined the pirates, he eventually learned from Nojiko that Nami was secretly working to buy the village’s freedom. To avoid burdening her, he pretended to know nothing of her true motives.

Throughout Arlong’s eight-year occupation, Genzou kept the village together, ensuring everyone could pay the exorbitant taxes and taking full responsibility whenever conflict arose between the villagers and the pirates. He organized secret plans for rebellion, once nearly being killed when hidden weapons were discovered, only to be saved by the intervention of Usopp. When Marine Captain Nezumi, bribed by Arlong, stole all the money Nami had saved, Genzou’s patience ended. He decided that the villagers would rather die fighting than continue living under tyranny, rallying them to march on Arlong Park. They were stopped by the bounty hunters Johnny and Yosaku, who insisted on giving the Straw Hat Pirates a chance to resolve the conflict. After Luffy defeated Arlong, Genzou met Luffy at Bellemère’s grave and made a solemn promise: if Luffy ever took away Nami’s smile, he would hunt him to the ends of the earth and kill him. Satisfied with Luffy’s response, he entrusted Nami to the pirate’s care. On the day Nami set sail with the Straw Hat crew, Genzou placed his trademark pinwheel on Bellemère’s grave, signifying that his duty was fulfilled and that Nami no longer needed the comfort he had provided since her infancy.

Genzou lacks any superhuman fighting abilities or Devil Fruit powers; he is an ordinary man with great courage, determination, and leadership skills rather than physical strength. He was easily defeated by Arlong and his crew in direct combat, but his true strength lies in his unbreakable will and his ability to hold his community together through years of oppression. He has been seen carrying a sabre and pistols as part of his role as sheriff, though his effectiveness as a fighter is limited. His influence, however, is profound. The pinwheel on his hat not only inspired one of Luffy’s attacks, the Gomu Gomu no Pinwheel, but also directly inspired the pinwheel portion of the tattoo on Nami’s left shoulder, a permanent tribute to the man who raised her. Genzou also has a humorous side, becoming flustered when Bellemère or Nami offered to repay debts in inappropriate ways. After the Enies Lobby incident, when Nami received her first bounty poster, he was outraged that the photo was too revealing, complaining to the Marines that it would attract marriage proposals and perverts rather than bounty hunters. Despite his protests, he kept a life-sized blown-up version of that poster on the wall of his police station, revealing the paternal pride beneath his gruff exterior. In later years, he continues to watch over Cocoyashi Village, reading news of the wider world with Nojiko and reacting with continued concern whenever Nami appears in provocative photographs.