Sang-min is a university student who, like most guys, likes women. Bo-eun is a high school student who likes to chat with her friend, and whose heart flutters when she sees a cute guy. These two hear shocking news from Bo-eun’s grandfather - that they have to get married. Grandpa’s long time wish is to see them get married, and now his illness is getting worse. 24-year-old Sang-min and 16-year-old Bo-eun have no choice but to grant her grandfather’s wish. Sang-min, though he married, couldn’t do anything to a 16-year-old girl who didn’t even have her first kiss. And now, he couldn’t go after older girls either. He decides to take good care of Bo-eun. But she runs away just before leaving for the honeymoon. He goes to Jejudo alone, and the newly weds there are getting on his nerves. Meanwhile, Bo-eun is having a date of her dreams with Jeong-wu, the captain of the baseball team that she had a crush on. Things get more complicated when Sang-min is assigned to Bo-eun’s school for the teachers’ field training. He wipes his face with Bo-eun’s underwear that he had mistakenly put in his pocket. And Ms. Kim bursts into their apartment, trying to get close to him. What’s worse, Bo-eun keeps dating Jeong-wu. Will these two be able to continue their married life?