The Hidden End is a ntr VN about two childhood lovers and the college experience seeking to tear them apart (or at least cuck the guy).
There's not a huge amount of content yet, but it seems to be going for a slow burn type of corruption. The events have been mostly of the accidental exposure type and the player receives a choice as to whether to watch or avoid them. However, there's not much sex content if you choose to avoid the rapey side of ntr.
The other issue is... why RPGM? The story is entirely linear, the only input from the player walking the sprite to the next scene. I think I spent nearly half as much time moving the character as I did reading text. I'd guess it was to cut down on the illusion renders in order to reserve dev time for writing or sex scenes. If it means development can occur more quickly and easily, I suppose it doesn't detract too much, but it's not great.
The horror aspect is has only been teased so far. Not my genre, but that's the way horror is supposed to work, right? The anticipation of fear can be worse than the reality.
Anyway, this game might be worth your time after a few patches if you're into ntr. The story and characters seem thin at the moment, but they might develop with time. The sex scenes are fine if you like illusion and ntr. Since I'm only into sharing and cucking assholes, it isn't for me. I wish Aedirn Studio luck nevertheless.