20 years ago, when he was 9 years old, Seonwoo-A from the real world swapped places with the Seonwoo-B from the video game. Seonwoo-A grew up in the video game while Seonwoo-B grew up in the real world.
Then they switched again at the beginning of the manga.
Now, we're seeing what happened to the Seonwoo-A when they did the original swap at the beginning of the manga.
I believe the first few panels are Seonwoo-B still in the video game after the reset. He has his Hunters stuff, but no memory of what happened, so he's back to being confused.

I'm fuckin confused