Han Seung-wan (Kim Jaewon) travels to Singapore to visit his first love, Lee Chae-young (Han Eun-jung). At the airport, he bumps into a young woman named Jung Se-jin (Eugene), and they accidentally swap passports. While Se-jin is on her way to the address listed on Seung-wan's passport, she meets Min Do-hyun (Lee Ji-hoon), who kindly gives her a piggyback ride. When Seung-wan and Se-jin finally meet at Chae-young's apartment, Seung-wan agrees to give back Se-jin's passport on the condition that she help him track down his missing girlfriend. To Seung-wan's shock, they discover that Chae-young is in a relationship with Do-hyun, whom she'd met in Australia. Heartbroken, Seung-wan goes drinking with Se-jin and turns to her for comfort, and they end up having a one-night stand in a hotel in Sentosa.