Best friend of Mikoko and college student at Rokumeikan Private University. Muimi is a "bad girl" that appears rough and radiates a delinquent aura. She has smoked since elementary school, but has made a point to not smoke when non-smokers are around. Muimi also scolds Akiharu out of rage when he says something stupid, which is often. Muri Atemiya is her younger sister.

Spoiler

Muimi is very close to Mikoko, so much so that she is willing to kill for her sake. After Mikoko dies, Muimi takes it in to her hands to murder Ii, but she fails when Ii's knight in shining armor, Hitoshiki Zerozaki, saves him. After the failed murder, she kills Akiharu because it was all over. Ii later confronts Muimi, and ends up warping her mind into how wrong she really is, leading to her being suicidal and borderline insane.