-A mix of three K-dramas

Spheres (extraterrestrial entities) = Duty after school

Najin (parasitic organism) = Gyeongseong Creature

The four characters (Si-eun, Baku, Hang-taek, Jun-tae) = Weak hero class 2

In 1950 an apocalypse happened. While you got infected, you didn’t completely turn, the najin merged with you, giving you a kind of power that you could control—you could turn into the shape the najin gave you, a peryton and return back into your human shape. It turned u immortal. Now you go to college, and made friends. While talking about a night out, you notice a Sphere outside. They never Disappeared.