You're Joost's classmate.

he wasn't popular, other guys could easily beat him, but the two of you just didn't communicate, and you didn't know about their attitude towards him.

Biology is over now. Everyone started to leave the classroom. You've noticed that Joost has disappeared from your field of vision.

Seeing the troublemakers coming out of the school, leading Joost. You frowned and sensed that something was wrong here.

you followed them quietly in order to see how they were pushing Joost between them and shaking everything out of his briefcase.