I can recommend these four side-scroller games, available on itch.io:
1) Xenotake ( https://vosmug.itch.io/xenotake ) - it's the game that inspired me a lot to do this project and its art style;
2) Ghost Hunter Vena ( https://vosmug.itch.io/ghost-hunter-vena ) - it's another side-scroller game from the same creator, it has more girls and content;
3) Primeval Planet: Angimanation ( https://linch47.itch.io/primeval-planet-angimanation ) - a sci-fi side-scroller game made by a friend of mine, it has complex controls, but more sex with monsters and other stuff closer to Resident Evil;
4) Zetria ( https://karnedraws.itch.io/zetria ) - this sci-fi platformer doesn't require the player to lose to unlock the scenes, and it's more focused on monsters, too.