Asexual horror/thriller novel where time keeps looping until you get with this other person except you're sex repulsed and very stubborn. Then it turns out that while the other person is hypersexual, they're also demi and completely understand you turning them down. So why does the time loop keep resetting when you turn them down or leave a bad impression on them intentionally? Well, the Killer,

When I exit the bar with my co-protagonist, finally understanding our relationship and that they have fragmented memories of me from each timeline which is what made them interested in me more and more over every loop, but we both can't remember what causes it to start over again, only to find a minor but constantly present side character I dismissed as annoying or odd outside with a gun