Isn’t it because the other Seonwoo died in chapter 59? In order for the world to not repeat with the keymaster raids and dungeon stuff, it makes sense that the original Seonwoo would make his appearance through the “hidden ending” created by the System.
I could be totally wrong, but this is just what I could understand of chapters 60-61. I agree that the way the information is presented makes this way more confusing than it needs to be, but maybe it will make more sense in the next chapter.

Can anyone PLEASE explain it for dummies? So there are two seonwoos basically and one of them was pulled into the world when he was Nine and then got back at 20. But what I don’t understand is:
What about the seonwoo weve been reading about the past 60 Chapters, was he Born in the normal world or guideworld and why does he never talk about this at all ? (⊙…⊙ )