Sensei

The homeroom teacher of Yuu's class and also a history teacher. He is quite direct with his students and he doesn't hesitate to compliment them if they work well as their "deprive" of summer holidays when the results are insufficient.

Spoiler

He is more attentive to Yuu and Kanemoto who are the worst students in the class. However, he is surprised by the sudden rise of Yuu's notes and wonders where his sudden motivation comes from.