Well, the first recommended game was "Goodbye Eternity", which is a typical Japano-VN clone with its onii-chan nonsense and the mother looks like 25.
And for "Mother NTR Training" - it appears to be the exact opposite of this game.
I agree, but like I said its the only game I've found so far
But then again I don't usually play games with darker sexual tones (usually leave that for doujins)
Of the sexual scenes in this game, only one of them has the protagonist get some real action, one is sleep groping, and the other two are just watching others, and some scenes are family. By this count, voyeurism and family are the current majority of this game, hence why I suggested those games.
And if you're saying opposite of this game, then what would this game be considered? I can't really come up with a set genre for it.
I haven't really found any games with voyeurism + incest + unaware sex, at least none that are rated well.
Like if you just want sleep/drug/unaware sex part of this game, Life's Payback is there, but its koikatsu which probably won't be liked by people that like Deathables.