But the killer doesn't bat an eye to kill Doha and the latter doesn't really seem to avoid confrontation either, which results in either kill or be killed. If Doha had plans before becoming conscious, I don't think the killer was part of them. Maybe there's a deeper story to Doha and his relationship with the other characters that are key as to why he came and why he killed that person. Bada's character supposedly was only tagging along with his brother and wasn't really acquainted with the brother's friends, but Idk about the others. Bada's info on the game characters and their rs with one another is very scarce imo.
I think as enjoyers of fiction that we all know by now not to believe what we're told, and only to believe what we see. And even sometimes to question what we see. Have you watched the movie "scream"? I don't want to spoil it for people that haven't seen it, but we watch a character die to the killer, only for it to be revealed that he faked it and was in fact partners with the killer.
I don't watch horror too often, so I can't say how often this trope happens. But Nick Jonas' character in "scream queens" also fakes his death and is partners with the killer.

Ok, I've been really trying to think about who Doha could be this whole time and I've had 0 theories until now. I think he was supposed to be a twist villain in the game.
My reasoning is that he 1)randomly killed that one villager or whatever and 2)is capable of killing the killer and 3)we never see him die (iirc). I think the killer is his partner that he set up this whole killing trip with. It's common for a slasher to have someone in their ear, and I think that's Doha.
So you may ask, why did he kill the killer after Bada confessed? Since obviously he wouldn't know that the killer would come back after being killed, he genuinely wanted to kill the slasher for Bada's sake. I don't think that the slasher is someone important to him, I think he's a convenient pawn that can be manipulated. I think he's trying to prevent Bada from both finishing the game and discovering that he's the twist villain. That's also why Doha has this uncomfortable and eerie vibe to him, how chill he is with killing and accepting this whole situation.