My biggest problem with the game is there's no buildup to anything. The beginning of the game/prologue teases a lot about the GF hooking up with dudes, but then you're dropped into the game and can have her sleep with anyone. For me it's lacking that element of corruption. One day her boyfriend tells her he gets off on thinking about her with other guys, and she's just like "cool I'll fuck other dudes" just like that? That's not very realistic unless she's already into it which would push this more into NTR territory than NTS territory as it didn't take anything to convince her, so why wouldn't she start sleeping around behind the MC's back?
The only aspects the game is missing to be complete (gameplay wise not story wise) is raw dogging and then creampie. I'm not sure what story the dev wants to tell, but this one is boring so far.
It's unrealistic?
Of course it is, that's why it's a fantasy...
Realistic is your GF/Wife is already cheating on you and now happy she can do it with your permission...
Or, she thinks you're a loser for wanting to see her have sex with other dudes and she goes full cuckold mode before leaving/divorcing...
This GF is the fantasy...
Understanding, loving, respectful, willing to explore the fantasy while agreeing, setting absolute boundaries that don't get crossed... The risk of losing her is low (right now) and she's still all about the BF, who isn't portrayed as a weak, stupid, pathetic, small dick loser who sucks in bed...
The GF actually loves him and thoroughly enjoys sex with him, holy crap, how rare is that in these stories?...
The buildup is not slow burn corruption (thank goodness), but she doesn't just jump in the sack with all of the other dudes...
After learning about the BFs fantasy, she thinks about it, there's discussion, she teases it, she's hesitant, seeks permission, reassurance from BF that it's ok, and she's clear, supportive, and enforces boundaries... I agree, very unrealistic...
And yet, it's not so ridiculously (porn logic, corruption) unrealistic, and that may be why it's a "boring" fantasy for some, which tends to happen for them when boundaries are respected and expectations aren't subverted...
Personally, I find this VN utterly gratifying.