Cain is on a rampage, demolishing lesser demons left and right. He's just discovered his most trusted general Sid's betrayal. Now aware that Sid might have his rival Satan's ear, Cain tries to protect his beloved door, Kyungjoon, from danger by leaving the human.
The king, however, did not count on Kyungjoon's longing to be reunited with Cain. A yearning so strong, it even pushes the human to potentially jump to his death, confident that Cain will appear when he needs him the most. But will the demon king truly be there to catch him?