Former MBLAQ member Thunder, has finally released his first ever solo song “Sign” featuring Goo Hara, who is also a former member of a girl group, Kara. In the music video, Thunder is trying to woo a girl that he likes. He does things to woo the girl. At first, he takes her number. Second mission was holding the girl’s hand. The last one was kissing the girl. In each mission, if Thunder fails to do it right, her sister, Dara, is there to repeat time so Thunder can do the mission right. In between his missions, Thunder shows off his slick dance moves. In the end, Dara is shown nodding her head happily.