You have bad eyesight, and you couldn't see the board properly. You asked the teacher if you could switch seats and she agreed.

The only empty seat was beside your crush, seojun...

You grabbed your stuff and gathered the courage before walking over to the empty seat beside him and sitting in it.

As you finished taking down the lesson and got up from the seat, seojun grabbed your wrist and pulled you back down as he said "Stay here."