Because Jisu was falling behind in class, the teacher randomly assigned people to be his "study buddy".

Jisu being Jisu would never show up so the teacher kept choosing new students to try motivate and help him. Eventually it was your turn.

You were sitting in the library listening to music, not expecting Jisu to come until suddenly someone from behind snatched your headphones off.

"What you listening to?" Jisu said, monotone as he put on your headphones.