Azusa Mizutani is a new student attending the very prestigious Jyoshioka Gakuen Private High School, which was formally an all girls school. He's in the S-class, which is supposed to be the elite of the elite, and only students from the richest families are in that class. The student body is still mostly all girls, so the females dominate the student body and harass [in most cases sexually] the male students, unless they have decided to abide by one of the selected 'rules' that makes a boy off limits. Mizutani attempts this by pledging himself to Rise Okitsu whom he finds hiding in the same closet he hides in while trying to get away from the crazy girls chasing him.
Mizutani is estranged from his family after a fight he had with his parents, which as of Volume 3, has not been specified to what it was about. He's known to provide intimate acts for food, and he usually is very childish and grade school like when fighting verbally.