Ynso, Mienyun, and Hyendju move into rooms of an old mansion owned by a mysterious master who calls himself the Master. The girls don’t know that he isn’t a human at all, but a demon tasked with collecting human pain and darkness to maintain the world’s balance. For his goal, he stops at nothing: first he seduces them with promises of happiness and brings their first love back into their lives, and then he takes that happiness away—turning loss into a source of energy he needs. But behind the flawless mask of the Master, there is something more—a secret capable of overturning everything they thought they knew about him and revealing what secrets he keeps deep within his soul.