Assassin and Sister

Jade Kimiko is getting ready for New Year's Eve with her friend Thea Summer over when her stepbrother Victor Ray wanders into the kitchen and starts groping her like it's nothing. Thea notices, Jade explains, and the explanation is that she's his free use stepsis. The game treats this as a starting point rather than the whole story, then pivots into a bullet-heavy adventure about saving the world.

From there it's a top-down shooter built for open-ended exploration, so you're moving between the domestic setup at home and combat sections where the shooting mechanics carry the pace. The two halves sit side by side rather than blending, and the game seems fine with that.