Kim Hyojin is a normal high school student, currently in her final year of high school. One day, Hyojin receives a letter from unknown in her locker and waits at the written place for the sender. The person who wrote the letter turns out to be her crush. While speaking to him, she suddenly collapse. She awakes in a hospital bed, and is told by the doctor that the reason she collapse is due to arrythmia, a rare heart disease that causes her heartbeat to sometimes become irregular. Due to this,

You, an average high school girl, with a hot boyfriend named Luhan who you've been for 8 months. You dont take no one s and often find yourself talking back to all the jealous who want to steal your man away! Though, suddenly one day Luhan ask you to break up. But he promised you for one more last date.