M.I.B MV Teaser

I guess Busterz are all waiting for this,right?

You do well first/Worried About Yourself First

MV Teaser Link: http://www.youtube.com/watch?v=yOUDHCHh9gs

I keep repeating this teaser

I like it so much and anticipate for the song to release

I'm curious who's the mystery singer M.I.B featuring in this song?
The beautiful model in the music video is Lee Ho Jung