Im left with more questions. What happens to the other guy? Why did they lose memories and...

That other guy became the sacrifice so he aint gonna be present there bada is a npc who just turned/came into human world so ig he remembered while the "humans" forgot all abt it.. idk who is the shitty mastermind tho

The lack of explanation for the paranormal wouldn't have been a problem if there wasn't that much emphasis on the fact that it is a game.
If it's a game then someone designed it. So we're left with more questions than answers. How did they enter it ? Who made it ? For what purpose ? What's the point of making a game the players forget playing ? How can a game modify reality ? And so on

I think it makes sense that we don’t see what happened to the game because we’re following the pov of the characters who got out of the game. My theory is that Pi Seongchan is still stuck within the game (like Pi Bada used to be) because there always needs to be a sacrifice at the end of the game. As for why or who set this up… it’s probably another literary trope. It’s not like in the Groundhog Day movie it’s ever explained why the main character is stuck in a time loop, he’s stuck in a time loop because the plot demands it for him to grow as a character. Similarly, in this story, the characters are stuck in a game that follows horror movie cliches just because it’s part of the plot, it doesn’t really need any explanation. You could even argue that being stuck in the game was what made Doha grow as a character, he went from being an asshole who cared about no one, to being slightly less of an asshole who cares about his lover lol. And Pi Seongchan, who cared about no one and was an asshole until the very end (unlike the other characters in the group who all tried to co-operate), became stuck in the game presumably forever because he refused to change. But also none of this matters because this is a BL and the focus was the romance so I’m sure the author didn’t think about it too hard lmao