Yoru no Gakkou e Oide Yo!

From Intercross:

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 saw her classmate feeding a duck.Her classmate is the most scary guy. But she found himself not scary at all. That time is when her love story begin