Sung-eun, who was on the phone at a park near her house after work, loses her earbuds. Sung Eun, who returned to the park where the streetlights were turned off to find the earbud, faces something that is not a person. At the same time, Gwang-seop, who can see things that are not human, comes to the park to take care of the park toilet. He spews venom as if to kill someone, notices that something that is not a person who was always in the same place is missing, and heads to find something that is not a person.