Summer Memories is a life sim game for adults with hot 2D hentai sex scenes, developed by Dojin Otome & Kagura Games. The game Japanese with English translations.
Take the role of a young male protagonist who's family visit in the countryside turns into a 30-day long breeding fest as you explore your relationship with your aunt and cousins.
Current version: 2.03 Deluxe Edition (completed).
Multiple playthroughs would be needed to find all different endings, providing many hours of gameplay.