Would be easier if you defined what you consider "hidden". But here are my favs that don't appear within the first 5 pages of views.
iNSight of you - best damn trainer there is, if you like hard maledom. Funny dialogue, and almost everything is animated.
Star Knightess Aura - not to be confused with the legion of Japanese RPGM games that revolve around raping the MC six ways from Sunday. Best female-MC slow corruption game, albeit with a mind-control flavor. Also solid JRPG gameplay.
The Curse of Kubel - falls into the aforementioned category of JRPG rape games. But it's exemplary, with a good localization, decently written, and pretty impressive use of the engine. Good NTR corruption, though of course they had to kick it off with an unnecessary rape.
Hero Party Must Fall - very promising netori trainer. Writing is well above-average for a smut game.
Corrupted Saviors - Hard non-con corruption with a lot of player agency and replayability.
