Cortis burst onto the scene with their pre-release single, "Go!" BigHit Music K-pop boy group Cortis is not even two months into their career - but it's nearly impossible to tell. The five-member outfit is the first boy group to debut from BigHit Music - the home to supergroups BTS and Tomorrow x Together - in six years. On their first official trip to Los Angeles as a freshly debuted group, Cortis seems to be taking everything in.