Hiromi Masuoka is a student at the Ichieda Gakuen Private High School attended by Koyuki, Saku, and Chiba. She also worked for a period in a doughnut shop next to Koyuki's, the Seiryuu restaurant, but was fired after blundering and causing a mess (on which she does not elaborate). She is a friend of Saku and Koyuki, with whom she learns to play the guitar.
