Sungmin tries to be a good friend for someone who has helped him. But the new student who's named Kyuhyun, acted as if he attracted on Sungmin. But sometime, Kyu like wanna kill him. Sungmin doesn't understand with the change of his nature that changed so fast and very scary. Then,,  The identity that being a mystery and his  past slowly revealed.

As a player, A dark and empty cover his heart. Until came someone with a little shine. A shine that changed the whole world of Ryeowook. he called him 'firefly'. Ryeowook and Donghae are be friend. Too close and too beautiful. but then,, the friendship is change since Lee Donghae said that he loves Ryeowook.   And,, they can't be together anymore.   What's happen??