It's been two years since Kim Namjoo saw her all-time crush, Kai. She came to his high school to accomplish three missions: 1) To see her childhood friend, Bae Suzy; 2) To meet the girl who saved her from being bullied in kindergarden, Krystal; and 3) to be Kai's girlfriend by the time he graduates from high school. Having a crush on him since middle school, she studied hard in order to enroll into the prejudious school.