One day, the protagonist, An, finds himself inside a horror-themed 18+ game, with no way to leave for now.
He has no family, and no close friends. He likes staying at home, so no one notices when he vanishes from the real world.
An is an ordinary new player. He's just a little calmer and more perceptive than the other newcomers, that's all.
At first, none of the veteran players know who he is, and no one pays him much attention. Then one day, the game rankings refresh, and the name at the top of the player ladder is a single character: An.
Only then do the veteran players realize in horror that this person named An has been lurking behind the scenes in every instance they've entered, right alongside the bosses.
An: Ah, I'm just playing a game.
I accidentally became a boss along the way.
He pushes up his silver-rimmed glasses and vanishes into the darkness.
Pairing: An x an unnamed Primordial God, boss player x game System
Content warning: The protagonist is the seme! The protagonist is the seme! But it's a clean romance, and the perspective makes no difference.
Theme: Don't let games become an obsession. Play in moderation and enjoy yourself.