Do Do-Hee, played by Kim You-Jung, is the successor of the Future Group. When her life became endangered, she got into an unexpected entanglement with Jeong Gu-Won, a demon portrayed by Song Kang, culminating in a contract marriage that significantly alters her life.
Jeong Gu-Won, an immortal demon, sustains his eternal existence by striking perilous yet enticing agreements with humans enduring torment. Disdainful of humanity, he has prowled the world as a dominant force for two centuries. However, his sudden loss of power occurs upon involvement with Do Do-Hee, leading him to form a contract marriage with her to avert his impending extinction. His survival now hinges on safeguarding Do Do-Hee, who inadvertently absorbed all his powers. Amidst these circumstances, their bond evolves into a romantic relationship as they navigate the complexities of their situation
