SPOILER: Yoojin's Kid Explanation

I think there have already been comments about this, but seeing all the comments on this chapter, I'll explain again for anyone who wants to know and hasn't seen yet.

In Chapter 89-93 (Novel Chap. 103-105), Yoojin has the encounter with Diarma. Yoojin defeated Diarma and gained the magic stones.

In Chapter 96 (Novel Chap. 108), Yoojin cuts his chest and to put the magic stones in. Since Yoojin has the Caregiver abilities, he's able to create another being with his power and the stones. (idk if someone can explain that better than i can)

Then in the novel (chapters 140-143), Yoojin visits Sung Hyunjae. If you remember, Hyunjae is one of the people who is very sensitive to the change. Basically his memories pre-regression are refusing to be "absorbed" to the Hyunjae now. So he's pretty much rejecting himself which caused some problems with himself where the pasts self kind of took over for a bit or something (I can't explain it really well). That led to confusion and Yoojin being dropped in an aquarium...but anyways, Yoojin used his mind skill from Diarma, and he was able to talk to the fragment of Sung Hyunjae (pre-regression memories).
The fragment of Hyunjae says that he doesn't want to disappear, but he isn't the main host so he's fading. The fragment wants a new body, in particular the one that Yoojin is "growing" (is that the right word?). Yoojin is obviously like no, but Fragment Hyunjae says the stone is cracked so it won't work properly. If Fragment Hyunjae goes into the stone, he'll be able to make it work. So, that happens.

The first appearance of Yoojin's kid is in chapter 271 in the novel. The kid doesn't have a name at first, Yoojin just called the kid Changeling (because that's what the kid is)

Sorry if this is long and made no sense