Jaekyung is known as the famous MMA fighter from the country, he got lots of achievements as an athlete, sadly he chooses to get an early retirement because his injury on his shoulder makes his performance not as great as before, and the recovery period wouldn't be optimal if he continues to fight in the tournament at that situation. Jaekyung and seerim met at that dark hallway near his house, she's still a student while he's already on his three stages of ages, she's just an immature girl.