Dormitory 2, 2nd year. A high jump athlete whom Mizuki admires. He is Mizuki's roommate and realizes she is a girl early on due to an accident shortly after her transfer. However, he doesn't tell her that he knows and often ends up looking out for the somewhat clumsy Mizuki. He had quit high jumping after an accident where he protected his middle school manager, but influenced by Mizuki, he returns to the sport. He has a cool and blunt personality, but is kind at heart and very popular with girls due to his good looks. He dislikes sweet foods and can lose consciousness if he sees something extremely sweet. He is a lightweight with alcohol and becomes a compulsive kisser when drunk. As he gets to know Mizuki, he develops romantic feelings for her. After Nakatsu confesses to Mizuki again, Sano and Mizuki finally realize their mutual feelings. When the three dorm heads find out Mizuki is a girl, he confesses to her that he knew all along.

Dormitory 2, 2nd year. Originally from Osaka, but speaks standard Japanese. He doesn't know Mizuki is a girl but falls in love with her anyway, leading him to worry that he might be gay. He isn't great at studying, but having entered on a soccer recommendation, he belongs to the Osaka Gakuen soccer club despite knowing they are weak; his dream is to become a professional player. He has a bright personality and is the class mood maker. He is quick to pick a fight and is often mistaken for a delinquent based on his appearance, but he is actually friendly and good-natured. He calls Himejima by his real name, Masao.

Head of Dormitory 2, 3rd year. A handsome playboy who loves women, but has a friendly personality and cares for his juniors. He was kind to Mizuki when she first entered the dorm. He possesses strong leadership and is overwhelmingly supported by his residents. He is constantly competing with the heads of Dormitories 1 and 3 whenever there is a school event.

Head of Dormitory 1, 3rd year. A pure jock type who is as hot-blooded and straightforward as he looks. However, he also has a surprisingly sensitive side. He views Nanba as a rival and often comes to Dormitory 2 to declare war before school events.

Head of Dormitory 3, 3rd year. A narcissist with an incredibly intense personality. He hates the name Masao and calls himself Oscar M. Himejima. He claims to be half-German, but is actually a pure Japanese man born and raised in Japan. He is always competing with Nanba and Tennoji, but they mostly ignore him, and even Mizuki and the others treat him lightly.