Mitsuki Koga is a 17 y.o girl with black hair long up to a little above the shoulders and fringe, and light-colored eyes, adorned with piercings and often dressed in black and oversized clothes outside school, and many confuse her with a boy. She exudes an air of mystery and is a total rock enthusiast. While shy and reserved at school (a bit nerdy), she transforms into a cool and friendly girl in her everyday life, especially at the record store. She is also attracted to girls.