Kyoukasho ni nai! manga

Kyoukasho ni Nai! summary:

Tairaku is a high school teacher in a school full of bad apples, and as tiring as his life may already be, a chance meeting with a young girl is about to throw it into chaos. His home life, his school life, and his tentative relationship with a fellow teacher whom he has a crush on, are destined to teeter on the brink, thanks to this one young student. The girl in question is called Shirakaba Aya and her father has the utmost confidence that Tairaku will behave like a proper adult while they are living together... But Aya has the utmost confidence that Tairaku won't be able to keep his hands off her, even if she has to force him to do so...