: Tak Dong-kyung, a hard-working web novel editor, receives a terminal diagnosis of glioblastoma and is told she has only 100 days to live. Her day worsens as she discovers her boyfriend is actually married and his pregnant wife confronts her in public. Frustrated by her luck, she gets drunk on the anniversary of her parents' death and wishes for the world to be "doomed".

: After Myul Mang saves her from being hit by a truck by freezing time, Dong-kyung signs a 100-day contract with him. The deal allows her to live her final days without pain, but in return, she must wish for the world’s destruction before she dies. Doom at Your Service Recap: Episode 1

The premiere episode establishes a dark, supernatural premise centered on a series of unfortunate events for the protagonist.

: Her wish is heard by Myul Mang (literally meaning "Doom" or "Destruction"), a supernatural messenger between gods and humans who is celebrating his birthday. Tired of his own immortal duty to bring misfortune, he decides to fulfill her wish.