Can someone help me name this story?!

So it starts off with this girl, who's Changmin's girlfriend (DBSK) and got him a watch for thier 2 Year anniversary i think. She calls him up, but he doesn't remember things like these and blows her off. He doesnt contact her for a week or two so she goes to his apartment. Upon opening the door to his bed room, she find him and a girl who's almost I think o.o uuhh yeah, so She runs out crying and drives home. Of course, he follows her there, only to arrive right as she enters her house. Going up to her door, which is either unlocked or he knows where the key is, which makes him want to laugh at her cuteness.. but stops because of the seriousness of the situation. Uhh so R-rated, I guess they ended up doing it.. In the end he's very remorseful and sorry for what he did.. and I thats all

Please someone help me find this story! It really wasnt bad at all(: I hate how I suddenly cant remember the name and such. Please!