Mami Mizuno is Shigure Kitami's childhood friend and seems to be quite possessive about him as she seems to get angry whenever she sees his shy expressions when Yukina Himuro's around. She seems to know about Shigure's secret of carrying a student notebook which includes names of the girls in his class and which he uses to keep track of how many girls have confessed to him and what methods have been used by them. Mami doesn't seem to like Yukina much as she is able to bring about real feelings of like and love from Shigure, which again indicates that Mami likes Shigure.
Mami is also known to have a weak body and acts cute around everybody even though in reality she is evil. She even acts extra-friendly with Yukina.