It's not advertised as a non-ntr game. as a matter a fact. this game wasn't advertised as anything. It was never said to be pure vanilla or pure NTR. But it has been Vanilla focused from the start. i had broken it down many times how much NTR to Vanilla content there's been per chapter and NTR has always been a small %.
let me also put it this way, since you called out the last chapter being 40% NTR (we don't even know for sure) making this game NTR.
if the first 12 chapters were 20% (and they aren't) with the last chapter is 40% NTR.
say we have 12 beers we are mixing together at 20% alcohol. we add in a third bottle to the mix with 40% alcohol. the entire mixture doesn't suddenly become 40% alcohol. The alcohol total is now only 21.54%. The total game is still much less NTR then it is vanilla.
Again though, it was never advertised as non-ntr. we knew NTR was in the game since CH1 and polls from CH 1 and 2 on patreon were voted to keep NTR in. the support for NTR has always been strong from the start.