MovieGuys
Parayste:The Grey is a spin off of Japanese Manga series Parasyte.
Like most Korean series, this one is competently done. There's a balanced mix of sci-fi/horror/action off set by quality character development. As a consequence, this adaptation has a depth and sense of realism, you don't always find, in series of this kind.
There's a nod to Invasion of the Body Snatchers, which is the most obvious point of comparison. Special effects are well done and further build the atmosphere of a normal world that's suddenly faces a familiar and at the same time, alien, other.
In summary, a worthwhile watch, if you like science fiction, action horror series.