Hmm..alright, so I was browsing through my YT feeds page, then I saw this.
credit: teliaia (as on sidebar) + ilovedoubles501@YT
HyunJoong raps for this song. Hmm.....this is not first time that he is sort of 'secretly' collaborating rapping outside.
I wrote about that like....2 months ago. (oh no, I cannot find it -___-)
Here
Title: Deflow Inc - Ft. SS501 Kim Hyun Joong, Park, Jo-Kyo, Jam2Y, Kwang Soo
Me post up first ; it's really short
@3:09 (hyunjoong corase voice 냐) + the end
Title: I Want - ft. HyunJoong
credit: lovetop7@YT