Responses
Doha being the main player fits for me. Because at the beginning he played the role of a heroic character then when Bada got entangled with him Bada realized his moral compass is a bit skewed. Like killing without batting an eye. Also killing other random characters like the first time when Bada sneaked a peek. Maybe Doha was strategically playing with one character at a time and Bada is the last one on his list to observe
My theory is, Doha is a player, who doesn't know he's a player. What I mean is that Dreadful Night is a game where NPC Bada has knowledge of the game and only when interacting with him can the player advance through the game.
Think about it, since Doha is the only one able (to our knowledge) capable of killing the killer, he is the player. But why can't he remember anything before Bada told him that they are inside a game and all of that?
Bada is an NPC (I think Bada said he can't remember anything before the whole game thing) whose settings and background story is knowing Dreadful Night is a game and who knows information about the game and that has been trying to scape from the game.
The whole scenario might be that only when interacting in the correct way with the correct NPC, can the player advance.
The player has to have the restrictions of repeating the game endlessly without knowing until they can get information from NPC Bada Lee, then that's when the true Dreadful Night starts.