Gouzaburou Seto

Gouzaburou Seto leads the mermaid Yakuza of the Seto region. An intensely overprotective father, he initially takes on a teaching role to keep a close eye on his daughter, Sun. His primary objective is the elimination of Nagasumi, a boy he loathes and frequently fantasizes about killing. Despite this deep-seated hostility, his cold demeanor gradually softens as he develops an unexpected bond with his students.