Fraternity heartthrob Kim Jongin is single again after ending a four-year relationship with Junmyeon, a meek political science student.

Junmyeon can't believe that he wasted four years on such a horndog so Junmyeon unexpectedly turns to Sehun, the charismatic playboy of another fraternity and Jongin’s childhood nemesis. Junmyeon asks Sehun to be his fake boyfriend to make Jongin miserable. Sehun is reluctant—but after realizing how distressing this could be to Jongin, he agrees to Junmyeon’s terms.

While in the midst of all this, Jongin’s close friend, Yixing, can see nothing good resulting from this, especially when he knows that his heart will be broken once again by Junmyeon.