Nasty Nasty release their music video for their first song together, “Knock.” It’s been revealed, “On September 3rd 2014, KEVIN from ZE:A, KYEONG REE from 9MUSES, and SO JIN, a rookie from Star Empire to debut in 2015, formed a special unit and put themselves up for a challenge. The unit’s name, ‘Nasty Nasty’, comes from the American slang ‘Nasty’,…