It was revealed that long before the drama began airing its first episode, the main theme song "Even A Little While" had been in its preparation stages, with the staff desiring Hwang Chi Yeol's voice over any other's for its husky power. Coincidentally, Hwang Chi Yeol also used to be the vocal teacher for INFINITE, and recently praised INFINITE member L's acting in the drama. 

Listen to Hwang Chi Yeol's OST and recap key moments from 'Monarch - Owner of the Mask' above!