You can try this one:
https://thef95zone.info/threads/tsrpg-my-doki-doki-transexperience-v1-0-milk-angel.11479/
Also this VN:
https://thef95zone.info/threads/absolutely-haunting-v0-3-16-mindshard-studio.4003/
This rpg/vn has that in one of its routes:
https://thef95zone.info/threads/adventure-high-v0-84-changer.1556/
This also has that in one of its routes but its not my kind of game so its just a suggestion:
https://thef95zone.info/threads/a-spell-for-all-v14-14b-cmacleod42.571/
Very early build but the whole game revolves around it:
https://thef95zone.info/threads/hex-v0-0-5-alpha-outsider-artisan.166142/page-3
A short html:
You must be registered to see the links
Havent played this mod but the base game is ok:
https://thef95zone.info/threads/jikage-rising-possession-mod.66078/
Minor mechanic:
https://thef95zone.info/threads/re-curse-origin-v0-6-gratuitouslove.178139/
Student transfer could have some scenarios about that.
One route and very short:
https://thef95zone.info/threads/parasites-of-evil-v0-15a-seafix.82972/
It has that but its just a bad ending and a minor mechanic from an enemy:
https://thef95zone.info/threads/moncurse-v0-6-1-2-kamuu.181543/
this one just has one enemy and a bad ending near the end:
https://thef95zone.info/threads/mercanoid-v1-0-7-pyksies.170945/
this one is not nsfw:
You must be registered to see the links
one or two enemies centered around that:
https://thef95zone.info/threads/house-of-pandemonium-unity-edition-v1-0-11-throwawaylady.47776/
Not such a good translation and confusing besides that the entire game is about that:
You must be registered to see the links
(the same link)
https://thef95zone.info/threads/rpg-possession-game.99647/
One game over (caused by an enemy) has it havent completed it, not my kind of game:
https://thef95zone.info/threads/steppenwolf-s-villa-final-dawn-is-eternal.158873/
Just the first or second game over caused by losing battles, couldnt complete it, stuck at the part of the enemy base infiltration:
https://thef95zone.info/threads/swan-song-of-the-white-angels-0-13-1b-h-ero.85178/
One story scene that has it, very very short scene:
https://thef95zone.info/threads/the-last-necromancer-v3-5-bandai_.165594/
A vn, too boring for me to end, idk if it has it but its tagged sooo:
https://thef95zone.info/threads/tsukihime-type-moon.11897/
This one has (some very minor kind of) incest, but its completely optional:
https://thef95zone.info/threads/najima-island-v1-0-0-velzies.156066/
And thats bout all i know, if you find more pls tell me i also like possession