The Target of MT

What do we do at an MT? Min-hee and Min-soo used to date. Dong-hyeon and Ah-yeong drink with them the night before they go for the MT. Min-soo puts Min-hee to bed in a motel and Ah-yeong who had the hots for Min-soo, seduces him. They promise to keep it a secret but Min-hee finds out what they have been doing. However, Ah-yeong is a provocative one and decides to seduce Min-soo at the pension where all four of them are together...