One

In which Kang Yeosang starts his senior year of high school where he meets Choi San and Park Seonghwa. Choi San, a new boy at school with the best grades and someone who tries helping people in any way he can. And Park Seonghwa, the bad boy in school who's training to be an idol, gets the worst grades and doesn't care about anyone else's opinion on him, but secretly cares about what Yeosang thinks about him.

One day, Yeosang accidentally pushes Seonghwa, making him break his arm and lose two weeks of dance practice.

What happens when Yeosang feels bad about Seonghwa's broken arm and starts taking care of him, but San doesn't like that?