SM University is an all boys University. There is a rule that all student needs to obey and that is, LOVE is forbidden behind and outside the doors. Anyone caught having a relationship behind the Principal backs, will be expelled for good. The traditions were obeyed for years but when 3 boys from different backgrounds arrive at the University, changes started to happen with the help of the University newest Professor, Yunho.

He was there when they needed help. He was their pillar of strength and their hope. He never utter any complains nor show any signs of giving up despite people forgetting who he was. Who is he? He is a living legend. A sunbae who would sacrifice his time and his song parts to his hoobaes. A smile that brightens his hoobaes hearts in time of darkness. But what happen when the family pillar of streng