Sakurako’s Cuckolding Tale

A monster and its otaku accomplice take Takimaru hostage, and the price for his safety is Sakurako's agreement to become the otaku's girlfriend. That would be humiliating enough on its own, but a "curse of successful love" laid on her without her knowledge means she's genuinely falling for him as the thirty days tick down.

Sakurako plays along as the perfect girlfriend on the surface while working the case underneath, trying to find a way to Takimaru before the curse finishes what the blackmail started. It's a countdown she's losing even as she plots to win it.

You split time between Sakurako's side of the story and the men circling her, working through the village's sandbox and whatever puzzles stand between her and her friend, while the otaku tightens his hold day by day. The relationship isn't static; it corrupts on a schedule, and the ending you get depends on how far that thirty-day clock runs before anyone acts.