Kinda late but my favorite NTR game of all time is "TS Mahou Shoujo Nao" and its sequel. If you like NTR (and Netori), corruption, body modification, brainwashing/mind control (in a gradual way, no instant bullshit) then this is the holy grail for you. I'm still waiting patiently for the third and maybe final game in the series to come out. But even without that third game, the first and especially the second are absolute masterpieces. If the artstyle of the first game turns you off a bit still keep going, it vastly improves in the second one but you absolutely have to play the first game first.
Jinsei Tsukoudome's games that feature NTR are also all masterpieces.