Gaon Albums Chart
Later on April 8, 2013, "Romantic Spring" was released as a collaboration project between Gain herself and Korean singer , who later became her labelmate. The collaborative EP debuted at number three on Gaon Albums Chart. On April 13, 2013, she was featured in PSY's music video "Gentleman", along with the "arrogant" dance which was popularized in the Brown Eyed Girls song "Abracadabra". She then returned with Brown Eyed Girls' 5th studio album, "Black Box", which was released on July 25, 2013, and later appeared as a guest performer for IU's "Everybody Has Secrets" (Hangul: 누구나 비밀은 있다) on her 2013 release. In the same year Gain parted with LOEN Entertainment and joined the APOP Entertainment roster, while making her first major appearance in film with "The Huntresses."