You mean like Yandere AI Girlfriend Simulator. There's a ton of videos about that.
There is also discussions about how that would not be a very good idea for classical npc usage for various reasons. The ai, as the word used to be used for what npc do in a video game, does not benefit all that much from what llm gen ai can do. Or maybe they do, but it is used at a much, much smaller scale. It sure would make 4x games more interesting and other types of games where you play against ai players.