GyeongSeong Creature Part 1: What is the monster & the najin?

Inside the confines of Onseong Hospital, a sinister and chilling revelation awaits the protagonists of Gyeongseong Creature Part 1, unraveling the nightmarish truth behind a monstrous entity and the ominous najin.

This Netflix K-drama interweaves a historical setting of the Japanese occupation of Korea and a secret government faction hellbent on creating a new world order. Gyeongseong Creature Part 1 sees Yoon Chae-ok (Han So-hee) and Jang Tae-sang (Park Seo-joon) venture into Onseong Hospital.

Rumors circulate among the townspeople that the hospital has something to do with a slew of missing people. On the hunt to find a missing woman and Chae-ok’s mother, they venture inside and unravel the horrid truth between the government and the missing people.

Underneath the hospital lies a monster far too advanced and lethal, thanks to a parasite called najin in the Gyeongseong Creature Part 1 K-drama. But what is a najin and its effects?

Warning: Spoilers ahead!

Not everyone survives the najin in Gyeongseong Creature

The najin is a parasite found by the Japanese military that infects the human mind and transforms survivors into monsters. Chae-ok’s mother is the only known survivor. Or is she?

Throughout Gyeongseong Creature Part 1, very few details are known about the najin. Set in 1945, the K-drama takes place during the Japanese occupation, and the government uses Onseong Hospital as one of its secret labs. The missing people were taken as test subjects. A select few given the najin would survive.

In the first episode, three women are selected to partake in the experiment. Commissioner Ishikawa (Kim Do-hyun) sees something in an older, more resilient woman. They are taken into separate cells and given rice cakes and water. Unknown to them, the water is laced with an unseen parasite – the najin. Soon, two women begin to get sick and go mad. However, the older woman shows less severe effects and signs of change. Soon, she becomes the monstrous Gyeongseong creature.

Gyeongseong Creature Part 1 gives a better understanding of the najin as a small parasite that works its way into the human brain. It soon takes over the brain and takes control of its synapses. The result? Mutation. Najin turns humans into apex predators. But the K-drama doesn’t divulge its origins.

But who is the monster? It’s revealed that the monster is none other than Chae-ok’s mother. She was given the najin and survived the trials. It took over and turned her into the Gyeongseong monster. As the monster, she grew in size and mutated with tentacle-like arms from her back. She has heightened hearing and sight and can kill instantly. Above all, when dormant, her body has a self-defense mechanism of producing anthrax.

Gyeongseong Creature Part 2 dived further into the backstory of the najin. Kato tells the Yukiko the najin was found inside a glacier in the Muryong Snow Mountain where the Na people live. But he informs her the najon alone doesn’t create the monster like Chae-ok’s mother. The najin alone retains the person’s human form but become predators who hunger for human brains. They become volatile, have super speed, and can heal wounds instantly. They’re also sensistive to light, fire, and nitrogen.

Chae-ok’s mother was turned into the monster because she was injected with anthrax when given the najin. Gyeongseong Creature Part 2 reveals Akiko’s najin was passed on her newborn son.

Read more K-drama content here, Dexerto’s Gyeongseong Creature review here, and character explainers for Death’s Game here.