Synopsis: A grocery store worker (Jeon So Nee) gets into an altercation with a thug when he gets upset at her request to get the meat he picked up from the butcher price-tagged. The man is thrown out. Enraged, he follows her in his car and attempts to murder her.
Right when she is about to die, a parasite invades her body.

Thus, she starts her journey of symbiotic cohabitation with a monster inside of her that failed to take over her brain due to her severe injury. So now she has the power of the monster but the brain of a very simple, down-to-earth girl who considers herself unlucky in life.

Accidentally, Su-in ends up teaming with an on-the-run gang member (a delightful Koo Kyo Hwan), who hides in his hometown to lie low after a botched assassination attempt on some gang leader. His sister is missing, and the quest to find her has him stumbling into a horrifying ordeal that changes his life.

The parasite happens to be part of a large-scale invasion of organisms whose aim is to invade people's brains, kill them, and eat them. To survive, they must find a host.

One of the parasites invades a random oppa at a musical festival, turns into a flowery monster, and goes on a killing rampage on camera. This exposes it to a few intense individuals who now embark on a mission to eradicate it and its kin by forming an elite team called Team Grey.
I haven't read the source material, but it's nothing original. It's a regular zombie story where humans turn into monsters and prey on people while people with guns hunt for them.

What's great :
Execution. It's not over the top, screaming gore with blood flying everywhere for no reason. The underlying theme: Who are parasites? How are we different from them? Instead of telling us, the director shows us, and he has been able to make quite a compelling case. The action is done tastefully, the VFX is great, and none of the monsters are remotely scary. Most look like a cross between a botanical garden specimen and a Monster-Inc character. A few even turn into pretty flowers.

Gore-O-Meter : A couple of scenes might be a little disturbing for those who avoid crime thrillers, but as someone who has always tried to dodge blood and gore fares unless genuinely invested in the story, I was able to watch it all without the ff button. There are no useless torture or slashing scenes just for cheap thrills. And there are no creep factor or jump scares either.

I would peg the gore at 5/10.

Performances:

Jeon So Nee is excellent. She is terrific as the dual personality of Sui In and Heidi. Sonee evocatively blends the pathos of a struggling girl who is always trying to find a hand to hold on to and the apathy of a monster who does not understand her point of view but has little option but to go along with her choices. Their internal fights are subtle, and she manages to give an individual voice to each character with aplomb.

This has to be the...

fun little show! i love the anime but it's been years since i seen it so i can't recall much lol.

appreciated what they pulled from the source material but i also love the changes made! like shinichi and migi have such a different relationship than suin and heidi but both work so well~

i am praying for a season two with shinichi!! >_<

Ok, I know I am looking for logic in a sci-fi/alien movie, but it bugs me as to why the "worm" was able to make the body of the conniving police man move and talk when it had left the body. That is a huge plot hole which is the only way they can make the whole final battle work, so that was a little disappointing. I also find it funny though how the human bodies have to swing their head around to wield the alien tentacles. Does make them look a little silly at times, so that actually makes the aliens seem less intimidating! But still, a fairly fast-paced quick watch.