Mizu-chin is a supporting character in the anime and manga series Bokura ga Ita. She is a high school girl who becomes one of Nanami Takahashi’s closest friends, having known Nanami since middle school alongside their mutual friend Taka-chan. Mizu-chin is naturally curious and inquisitive; whenever something catches her interest, she cannot resist getting involved. This trait makes her an active participant in the social dynamics of her friend group.

Prior to Nanami’s relationship with Motoharu Yano, Mizu-chin harbored romantic feelings for Yano herself. Despite that past crush, she remains a loyal and supportive friend to Nanami throughout the story, often observing the ups and downs of Nanami and Yano’s romance with concern and involvement. Her own early affection for Yano adds an unspoken layer to her interactions, but she never acts on it after Nanami becomes involved.

As a character, Mizu-chin does not undergo a major personal arc; her role is primarily that of a confidante and witness to the central couple’s journey. She provides a grounded, sometimes gossipy perspective on the events unfolding around her, and her presence reinforces Nanami’s support network. There are no special abilities or standout skills attributed to her; her significance lies in her friendship and her unrequited feelings, which quietly inform her reactions without driving the main plot.