Mitsuki Yamamoto is a student of Byakudan Senior High School's classroom 2-4 and student council secretary.  She is also quite strict and likes to keep things clean and organized. Due to her merciless attitude towards slovenly men she is called “Hellgirl Mitsuki” amongst the male first-graders. As she does the chores at home with her grandmother, she is a very good cook. Her usual severe attitude might be a reflection of her motherly instinct.