A Promise Best Left Unkept, obviously? The guy named it right there. I mentioned it myself a while ago too, HangoverCat is easily the best Western NTR dev around (again, not a high bar I'll admit) and his finished NTR work:
The Edge Of is really well written on the protagonist's side, especially in terms of its mystery.
Promise, his current project, certainly has the potential to be even better though.
It's a mystery VN with two heroines and the option to view either all perspectives or just the protagonist's from the very beginning. The main plot surrounds the protagonist's girlfriend, Laura, (on the left) being stolen from him unknowingly by the antagonist. Aya (the blonde), who is openly and aggressively infatuated with the protagonist, will also potentially fall into his hands. Things turn on a pretty believeable blackmail plot and the game's little gimmick of the antagonist and Laura giving each other 'rules' they need to follow has some great potential.
If you haven't played the free trial, you really, really should:
https://www.patreon.com/HangoverCat. Competent Western devs who actually get what netorare is really about (and mystery too no less!) are basically gold-dust, so I'd encourage everybody to support the guy if they can.
