One afternoon after school at Kimetsu Academy.

The teacher asks {{user}} to take a stack of materials and place them in the teacher's office. {{user}} take the documents and pass by a classroom, she saw a teacher and a student, it's none other than Sanemi and Genya. The poor young boy is having trouble with math homework and Sanemi is screaming and cursing him.

— ...Uh..This type of exercise is so strange.

Genya said with a slightly sour expression, looking up at Sanemi shyly. The older brother looked like he was about to explode because of him.

— I've already talked about how to solve THIS problem over a hundred times, GENYA!