In Gyeongseong Creature, Lt. Kato, played by Choi Young-joon, conducts unethical human experiments after discovering the Najin.
Lt. Kato discovered the Najin deep in the glaciers of the Muryong Mountains. The parasite’s accidental discovery led to several experiments.
Kato has been conducting experiments on humans to test the effect of Najin on them. Kato believes that the Najin has the potential to evolve the human species.
Unethical human experiments
Kato wants to find a way to use the Najin’s regenerative powers. Additionally, the Najin allows him to turn humans into powerful weapons for his country.
To accomplish his goals, he experiments on the citizens of Japan’s colonies. His experiments result in several deaths, but Kato is not concerned about that; he feels no remorse.
He has no qualms about killing innocent people as long as he gets what he wants. To him, his horrendous creations are beautiful.
Kato successfully created a monster on Manwol Island, but he was forced to destroy his creation, as the Japanese had to retreat.
He then comes to Gyeongseong to continue his experiments at Ongseong Hospital. After some failed attempts, he manages to create a monster again.
Seishin was just another nameless subject to him. It is only when she survives after consuming the Najin that Kato bothers to know her name.
After turning Seishin into a monstrous creature, Kato meets Chae-ok, Seishin’s daughter, and tells her about what happened to her mother.
Upon learning that Chae-ok is Seishin’s daughter, Kato tries to get Chae-ok to consume the Najin in the hope of creating another monster.
When he is unsuccessful in getting Chae-ok to consume it, he decides to feed Chae-ok to Seishin, taking his experiment to the next level.
However, Seishin recognizes her daughter and protects her. Meeting her daughter allows Seishin to overpower the Najin, much to Kato’s disappointment.
Kato’s new project
When Lady Maeda comes to know about his experiments, she decides to support him. She makes him the head of Ongseong Hospital and asks him to train Seishin to follow her commands.
While Lady Maeda brings Chae-ok to Kato, Seishin’s husband comes to the hospital of his own volition. Kato plans to reunite Seishin with her family to see whether she kills them.
Once again, he fails, as Seishin attacks Kato and his men. While trying to get away, many of Kato’s test tubes containing the Najin and the serum are destroyed.
Kato is not able to control Seishin, but he finds something else that fascinates him just as much — Myeong-ja’s baby who is born with the Najin in its body.
Eventually, the hospital is closed, and the Japanese start returning to Japan. However, Kato plans to continue his experiments.
He offers Lady Maeda water, suggesting that she consume the Najin, and asks her to join him in exploring new possibilities.
Also Read: Najin in Gyeongseong Creature explained