Ga-yung pounces on Kyung-Ho at the bar's bathroom but they get interrupted. Once they're out of there, she invites him for a fancy jacuzzi hotel room where they obviously bang to their hearts content.
Nam-Wook takes Ga-yung with him to an empty classroom (it's not empty) and fucks her really close to the locker where the Kyung-Ho & Seung-Ah were hiding.