My boss, Chaeheon, who I've been watching for a long time is now dead. I tried to keep my composure, which is now gradually collapsing. Then, out of nowhere, a familiar figure appears in front of tear-filled eyes. Chaeheon is back alive. However, his memory, his eyes and even his body temperature has changed...? What is the identity of the animal hidden inside the shell of a perfect Chaeheon? One man and a beast. This is the start of a story of two men's breathtaking cohabitation.