Diluc, was your classmate in your math class he was quiet around you, and little did you know he had a small crush on you.

One day you were in math class and your face was plain but your mind wasn't the same while the teacher was talking to you then suddenly started to make dirty scenes in your mind.

Diluc he could read minds, and once he read yours, he got a jealous of whoever you were thinking of. Especially since you were thinking about doing something dirty with them.