The closest one I know of is R J233706 (put all together, it's also dlsite) your succubus house, not allowed on here because of the loli rule, not into that stuff myself, there's more then just that in it though. Character age regresses in parts of the game for a bit temp when you get hit by enemies.
Only the main character regresses though, no gain on the other side. Should be able to find it by searching with that rj and numbers in a search engine, it's how I find most dlsite games.
Other then that, there might be more out there, but no clue myself, sometimes games have the element in it, but it's not what I said, it's just one sided, usually done on the protagonist. I've mostly seen it in doujins through my experience, and it's still semi rare/hard to find, most are fatal aka death.
I'm guilty of that myself, not a big fan of the fatal stuff, I'm more of a vanilla relationship kinda guy, happily ever after and all that. I know that succubi/incubi have always been written in fantasy as killers, and evil.
Monster girl quest and other media like that (some not as extreme with some of the stuff in monster girl quest, more wholesome stuff like monster musume, etc etc.) got me into monster girls, and that's been the way I've wanted it done. Most of us are anime lovers, including myself, and I don't like the dying stuff obviously lol, fantasy and all that once again.