The app Love Alarm is created to notify users when someone within 10 meters likes them, without revealing who it is. Kim Jo Jo, a high school student who lost her parents at a young age, lives with her aunt’s family, which makes her life difficult. She doesn’t download the app because her phone is too old. Hwang Sun Oh, a popular student from a wealthy but emotionally distant family, attends the same school as Kim Jo Jo. His best friend, Lee Hye Yeong, likes Kim Jo Jo, and Hwang Sun Oh kisses her to confirm his feelings.