Sungyeol and Woohyun used to date in college but they broke up when Sungyeol fell for a girl in his graduate program and broke Woohyun's heart. It's now some years later and Sungyeol is divorced and has a baby. He moves into a new apartment with his child, and Woohyun discovers that his new neighbor, with whom he shares a balcony, is none other than Sungyeol.