Mimi is a normal schoolgirl who attends the same school as Illya.
In 2wei Herz!, she accidentally witnessed Illya and Kuro performing their Mana Transfer one day in school, which is in the form of kissing each other. Due to the lewdness of the kissing, she began to have lewd thoughts day by day, which became obvious when she was writing a romance story which turned into a gender-swapped boy's love story. Her story was later used by both her sister and Suzuka Kurihara for the publication of their new manga as a yaoi doujin.