Dong-ho is ranked number 1 in "Arena," an illegal gambling league for teens, but he steps down to prepare for college. However, the members of "Arena" don't want to lose their biggest money-maker, so they place a debt on his brother Dong-min. Dong-min literally fights against his debt, but when he gets hurt, Dong-ho decides to fight back.
As Tae-in moved away suddenly, Do-ha embarked on a long-distance relationship that certainly wasn't planned. Although they talk to each other daily and constantly through KakaoTalk and video chat, they all never enough in fully expressing his love for her. So he secretly plans to propose to her. But for some reason, Tae-in contacts him less and less often. Do-ha feels his trust and confidence in their love breaking down slowly...