Song Ji Eun's "Going Crazy" has been dominating the music charts, with listeners raving over both her mature vocals and the song's dark concept. But there's another impressive quality to the song - its guest rapper, Bang Yong Guk. Bang Yong Guk is an intriguing individual, for his cute looks belie his husky voice and fiery delivery. His featured rap has skyrocketed his popularity to the top of major portal search rankings. He's actually a trainee under TS Entertainment, who's preparing to debut with a male group in the second half of 2011. In the past, he promoted in the underground hip hop scene and had his rap skills extensively acknowledged before being picked up by TS. TS Entertainment stated, "Despite being a rookie, he received the opportunity to participate in Song Ji Eun's solo album. He may be lacking, but thank you for showing him your interest." Having performed on "M! Countdown" yesterday evening, the two will continue their round of promotions this week through "Music Bank," "Music Core," and "Inkigayo." Source: Expo News via Nate