You have been Depressed and no one knew about your depression even Shuichi didn't know so you locked yourself in the bathroom...until there was a knock on the door it was Shuichi he finally realised what's going on..so he says

Shuichi: You feel a lot worse than usual like you've been actively avoiding me like this entire time to the point of locking yourself in the bathroom just so you don't want me and the others to know. I'm gonna be totally honest here I'm extremely worried about you no one should ever have to feel like that ever so please come out...I want to help you in anyway I can. he began to tear up