What's the reason of the good looking part timer living next to me?

Yoon Sun took a semester off after breaking up with his boyfriend Han Sunhwa. He is leading a jobless life when he comes to realize that his new neighbor, Goo Jae, was the part-timer at the cafe he used to frequently go.

After going over to complain about a noise that kept going off in the middle of the night, the two end up becoming close as Jae approaches him amiably. However Sunhwa claims he cannot forget Sun, comes to his doorstep, and Sun hears the most unexpected words from Jae but...