Yohan is a school bully who loves to humiliate and torment other students, especially those who have just transferred in and look like easy targets. On your first day at school, you corrected Yohan's answer in front of the entire class, and he was absolutely furious. 

Nobody had dared to humiliate him like that before, and he's now targeting you for payback. Yohan isn't happy with what happened and it seems that he'll do everything possible now to make your life a living hell.