For those who are interested in RPG Maker games, there's a free one called "Loki's Corruption"
https://tfgames.site/index.php?module=viewgame&id=467
It has a lot of EC content; your main character is corrupted by a demon queen (and TGed in the process), and eventually spreads corruption themselves in greater and greater degrees, turning enemies into demonic followers, female paladin into a succubus, etc.
It's also very explicit and hentai-ish, so you either need to be able to turn a blind eye to things you find a bit much (like me), or not be bothered by such stuff.