Yamaguchi
Appears in the Shinobu/Sakura arc. Yamaguchi is a popular student and in the same class as Shinobu and Sakura, and the target of Sakura's secret crush. She goes on a mermaid hunt while believing that he loved Shinobu, when he'd actually loved her all along; however, this realization comes too late and Sakura is ambushed by the jealous mermaids and turns into one. After Sakura's disappearance, Yamaguchi suddenly begins dating Mana, leading Shinobu to suspect that she'd hunted a mermaid too, though it isn't confirmed. In "Condition to Return" (chapter 20): An unassuming Yamaguchi is captured and killed by Sakura, who is able to assume human form after bathing in his blood.
