After being abandoned by her‑of‑origin family, psychologist Vivian lives alone. One night, a black‑winged man named Killian drops down from the sky. An accidental kiss forges a life‑and‑death bond between them.By day, he is the amnesiac, puppy‑like Ian; by night, he reverts to his demon form, Killian. Starting with scientific therapy, Vivian gradually uncovers the truth of his betrayal by heaven. As they navigate their dangerous cohabitation, they grow fond of each other. In the end, they stand together to confront the mastermind Malachi. Killian abandons his divine rank and chooses to stay in the mortal world with Vivian.
