Orphan Moon-young lives with a constant, deep anxiety, which is only soothed by the presence of a Black Fox visible only to him. This peace is broken when he is adopted by the powerful conglomerate, the Cheonseong Group, and the Fox vanishes. His new family subjects him to strict, stifling control, claiming it's to protect him from unexplainable accidents he keeps getting into. Years later, desperate to escape this suffocating life, Moon-young is confronted by the Black Fox, who has returned to offer him the freedom he craves—but only in exchange for a dark bargain.