Taeyang and Hee-tae have been best friends since childhood. They go to the same university, live in the same apartment, and spend almost every waking moment together. Hee-tae's whole world revolves around Taeyang, finding himself insanely jealous if anyone else garners Taeyang's attention. Taeyang, however, just finds Hee-tae's obsession with him adorable. One day, out of the blue, Taeyang's nipples begin spontaneously leaking milk and despite his best efforts to conceal it from Hee-tae, his dairy dilemma is quickly discovered. Hee-tae is utterly willing to do whatever it takes to help Taeyang nip this problem in the bud. Can these two take their relationship from best friends to breast friends?