I think the other side (the village) is more of an alternate reality with different rules and timelines so what happened after they crossed that section that was blocked off in the end doesn’t affect the “real world” so bada was only supposed to exist on the other side and not in the real world and is still an npc.
Here are my theories! (If you're willing to read all this (╯︵╰,) )
Personally I understood the alternating realities kinda like what happened in "Alice in Borderland" (not exactly, if you know the show) in which they experienced a near death-ish event and then transported into an alternate universe with the same setting as the real world but kind of a "border" whether or not they actually do get to live in the real world or not. This is just my assumption though, considering that the game "Dreadful Night" wasn't explicitly mentioned as a thing that was occuring in the real world, but rather the system might've made them think so. Otherwise, what could have made them insist that it is a game in the real world with their memories becoming hazy and not recalling what actually happened to them in the real world (the crash) if not what I've mentioned?
As for Bada, I feel like contrary to him being non-existent in the real world due to being labelled as an NPC in game, he actually is an existing person! When Bada woke up with Doha by his side talking about the game and reawakening, Doha immediately asked him "Aren't you Pi Seongchan's cousin?", which implies that Bada DOES exist in the real world as Pi Seongchan's cousin but due to him not being directly INVOLVED in the crash, he isn't a main player in-game.
• "But how would that explain him being in the game in the first place? If he's not involved in the crash?"
- I do speculate mostly for plot convenience of the game itself. Or that he got into his own accident nearby the crashsite in the real world (to be explained further a few points below). Pi Seongchan's memories of him might've gotten him involved, especially with his character as the horror-enjoyer type who is also available to give Seongchan's Duffel bag to him.
• "He said that he was able to recall everything from the game because he was an NPC though?"
- This might connect to what I've said that since Bada was never supposed to be in the game/alternate Horror reality because of the crash, he would still be considered as an NPC in the game whose memories got transferred back to his physical real body.
• "How did he end up in the river near the site then if he wasn't involved in the crash?"
- I speculate that that's another thing! It might've been that coincidentally Bada also ended up in an accidental event nearby like a motorcycle crash by the riverbank due to the crash of the tunnel. This is suuuch a stretch though, but it's what I could piece together that made the most sense in my head
Of course, these are just my theories. Feel free to add on or debunk them hehe. I don't know what actually happened or what might happen after that, so I'm excited about the side stories!
so they weren’t in a game bcs the village exists in real life. which also means bada is not an npc…? this means they were just trapped in the village’s “space”? bcs if it were a game, the side story sneak peak implies that none of them actually managed to escape and they are all still in the game (although the village section is closed) or that the game’s influence is much larger than just elements within the game… meaning that it’s some crazy level supernatural thing they experienced..
i hope the author talks about the plot a bit in the side storiess!!!