SISTAR's Soyu and Giriboy collaborate with 'NO.MERCY' trainee Kihyun for 'Arm Pillow'

SISTAR's Soyu and rapper Giriboy joined forces with 'NO.MERCY' trainee Kihyun, the winner of the recent vocal challenge on the survival show.

The three also performed their collaborative song, "Arm Pillow" ("Pillow"), for 1theK's special clip segment!