From what the scientist told Lady Maeda, just the Najin turns people into something akin to zombie-like Myeong Ja. If combined with anthrax, it can turn people into monsters, like Chae Ok’s mother was. At the end of Gyeongseong Creature Season 1, when Chae Ok was on the brink of losing her life, her mother gave her Najin to heal her. The whole thing happened in a dream sequence, but it is safe to assume that this is what happened in reality as well. This also gives rise to a few possibilities.
First of all, the monster has been shown to be capable of intelligence and empathy. It may not have immediately understood that Tae Sang was trying to protect Chae Ok, but when the latter tried to save his life, she asked her mother to stop the killing spree and spare the man she loved. That is when the monster decides to let Tae Sang go. In many other instances, the monster has acted with rationality and intelligence, be it in the way they operated the lift or came through to protect Chae Ok herself. The creature was also known to release spores when resting as a way of self-defense. Our point is that maybe the monster understood its own biology and was not a thoughtless killing machine guided by instincts.
We believe there is a reason that Chae Ok, being given the Najin, was shown as a dream sequence and not as an event in real-time. The dream sequence allowed Chae Ok’s mother to be present in human form and not as a monster. That implies that she was acting with a mind that had considered multiple possibilities, one of them being that Chae Ok should not have the life of a monster or a zombie. If the monster was shown to have given Chae Ok the Najin, we would have assumed that it was operating with the primal need to see its offspring alive, in any shape or form. But seeing Seshin in her human form deliver the Najin makes us think that she was delivering proper medicine and not just a thoughtless zombie maker to her daughter.
The scientists have admitted that they don’t understand everything about the monster, and that includes the workings of its mind and its biology. But the monster may have been able to figure out things about itself. Maybe it knew which part of it was self-healing and which part of it gave it the structure of a monster. Therefore, it was able to isolate the healing part of the Najin and dispatch it to Chae Ok, making sure that she lived without turning into a monster. The only thing to suggest that something different happened is the ending itself. Tae Sang doesn’t seem to have reunited with Chae Ok. The obvious possibility is that he believes Chae Ok is dead and is struggling to move on. The second possibility is that he knows she is alive. The purpose of the dream sequence was to give the audience some food for thought. But practically, the monster must have saved Chae Ok in real-time, in front of Tae Sang. So, she is alive, and Tae Sang knows that.
Chae Ok killed Director Ichiro because she wanted to go back to the hospital, where both her parents were. She was driven by a need to take revenge for what had been done to her mother. If Chae Ok is alive and human, Tae Sang has already taken revenge for her. He set off the bombs that killed the villains and incapacitated the rest. Korea also gained independence, so there is nothing left to fight for. However, if Chae Ok turns into something other than human, Tae Sang may have had to let her go. This is not a strong possibility because that man is just not the type to give up on his loved ones so easily. But maybe he couldn’t deny her the request because of some unforeseen reason. That makes us wonder whether the monster (Seshin) is still alive.
Tae Sang and Chae Ok must have realized that the fight was far from over. Fighting the monster wasn’t just about patriotism but about doing the right thing. It has been a topic of discussion in Part 2 of Gyeongseong Creature a few times that people who only stand by and watch while evil is happening are equal to the perpetrators. Knowing the danger of cooking inside the hospital and choosing to evade responsibility for it would mean that they were encouraging it in their own way. This is the exact attitude with which they had both been fighting throughout the runtime of Gyeongseong Creature.
Chae Ok is definitely alive in one way or another. Another major clue as to her fate lies in the post-credits scene itself. Ho Jae (Tae Sang’s lookalike) was shown working for the government (most likely) in the present day, which is 78 years after the events of the series. Ho Jae was shown with a scar on the back of his neck, and when addressed by his name, he laughed. What about his name? It could have been funny unless it wasn’t really his name and one of many disguises that he was getting used to. Basically, he was laughing at the absurdity of the situation. Our point is that why would Tae Sang or his descendant (son) be alive if Chae Ok is dead? Chae Ok would have had to survive if she had given birth to Ho Jae. Secondly, assuming that Ho Jae is Tae Sang himself, why would he choose or come across immortality if he did not have anyone to share it with, namely, Chae Ok? In that case, the Najin has certainly had an effect on her body and, later, Tae Sang’s. Along with healing her, it must have given her immortal life or youth. Both Chae Ok and Tae Sang must have joined hands for a mission—to fight the monster—and that is when he even took the Najin. There has to be a lot more to the story here, which we are sure will be explored in Gyeongseong Creature season 2.