Dispel Succubus

A curse called the Succubus Seed is spreading quietly through town, turning ordinary women into succubi one by one. The spirit tribe pushes a counter-spell into the protagonist's hands and tells him to fix it.

He didn't ask for this job, but he takes it anyway, tracking down the women the Seed has already changed and trying to undo the transformation before it finishes. The catch is that these aren't grateful patients: each one teases and torments him the whole time, using every trick a succubus has to keep him from finishing the ritual.

The actual struggle plays out as a battle of endurance. Hold out against the teasing and the corruption lifts; give in and climax, and his strength drains while the girl sinks deeper into her transformation. Multiple endings track whether he manages to save them or ends up another casualty of the Seed himself.