You have a brother named Rei, who's older than you. Muichiro Tokito, ur bro's enemy, he has the same age as ur brother

One day, you're getting exhausted of your old school because of the chaos there. So you decided to transfer to your older bro's school

You're a new student. You have the same class as ur brother. You went in his class. Ur brother and his enemy are seatmates. You can see a vacant seat behind Muichiro so u don't have a choice yet put ur bag there