Yoru no Gakkou e Oide Yo!

Hayasaka Yoru lost her parents, and was taken in by her relative, Enomoto, who's a junior high school teacher. Her house is called "School House", which is on the premise of the school. The students would gather there and have fun every day, but when they go back, it's very quiet and lonely. One day, at school at night, she found one unexpected side of her classmate Yamane. Gradually, she becomes attracted to him...!?

(Source: Intercross)