15&’s debut single I Dream was released on October 5, 2012. The duo’s debut officially began on October 7, 2012, performing on SBS Inkigayo.
15&’s second single Somebody was released on April 7, 2013. The music video showed the two parodying the “K-Pop Star” judge panel while reacting to staged auditions/cameos by Park Jin-young and some of Park Ji-min’s fellow contestants from K-pop Star 1. On April 7, 2013, 15& made their comeback performance on K-pop Star 2 finale with “Somebody”. Upon its release on the same day, the song rose to the summit of music charts on Olleh, Melon, Daum and others.