Though single for seven years, Jung Jisoo is more than happy with her four precious friends: three vibrators and a dildo. But the morning after Jisoo takes her hot coworker, Han Sehyun, home after a company dinner, she's horrified to see him holding friend number one—a bullet vibrator! Yet instead of leaving, Sehyun is set on satisfying Jisoo's thirst by giving her what her friends can’t, and the two begin seeing each other. It seems Sehyun, however, wants to be more than just her fifth friend…