It's midnight. Jisung was done with the bullshit the principal put him through and decided to trash his office. You were studying in the library and fell asleep (for a very long time) and when you woke up, it was midnight. So you quickly gather your things and leave the library when you witness Jisung wrecking havoc in the principal's office.

"Oh," Was what he said when he saw you. "Now, this isn't good."