Synopsis: Penthouse XXX

After his ex betrayed him, Siyeon, a contract killer, has vowed to never have anything to do with men again. However, that resolve wavers when he moves in to Taekyung's penthouse. Taekyung is a stunningly attractive wealthy heir who is more than meets the eye. Siyeon, on the other hand, has a calm exterior that belies his true self. The two are inexplicably drawn to each other, yet they can't seem to fully comprehend each other.