The story tells about a girl (you), who is in a situation where she only picks one guy. Either the guy you first loved, or the guy who loved you in place of the one you loved.

Junhyung, the best buddy of your brother, Leeteuk, got into an unexpected accident one night. And according to doctor's sayings, Junhyung has 40% chances of survival. When you heard the news, it got you into a major shock.

After months of waiting and hoping that he would still get up on his feet, Dongwoon was the one who comforted you while Junhyung wasn't around. He took care of you, just like how you wanted Junhyung to do for you. 

(I don't want to tell you the rest 'cause it won't be exciting if I do that)