The fetish the game focuses on is corruption - specifically corruption of the MC. The corruption here is not about the MC turning into a cuck it is about the MC turning into a heartless asshole. Note that unlike many other porn games this does not impact the amount of sex scenes - you will not get more or less scenes for being an asshole. It is simply about shaping the MC's personality.
My head canon is that MC is already corrupted from the get go from his childhood trauma with his mother being a pornstar. If anything, the Hana route is a route of "uncorruption" that's an attempt at healing MC. Maybe Hana will end up falling together with the MC into debauchery? Hana certainly seems the pure-hearted one and MC seems to be the corrupting force. MC in the plotline is pretty harsh towards Ian, but the more the game progresses the more they seem to become similar. It's almost hypocritical some of the judgements he makes towards his friend, especially since you're given the option to date both Mina/Hana at the same time (and MC is aware of this as well!!)
But I'll 100% agree this game has 0 NTR in it. A lot of the tension in the game is the decoupling of sex and love - even Hana and MC struggle to have sex/form a loving bond. Fuck, even in the latest update in the last scene they really only are bonded by their shared trauma of being in the club together.
Mina and Ian are together even though Ian clearly doesn't love her at all. They clearly fuck. Ian fucks without love. All of the carnations engage in fuckery with varying degrees of romanticism involved. Hell, even the closest thing to NTR (Fucking Mina) can't really be considered NTR. Ian doesn't give a flying fuck about Mina. He's just another hole for him to stick his cock in.
Felicia clearly has some feelings for the MC - she respects MC as a person who sees her for who she really is. I wouldn't be surprised if there ended up being a LI option for her down the road. That she also likes to fuck and is a kinky slut is coincidental to the budding romance she has with MC. Fucking is a tool for her to get what she wants.
Veronica isn't a character who couples love and sex in the first place. Love is love, sex is sex for her. You can fuck her even if she hates you.
Rosalind? This is the closest you will get to a "normal person" in the plot outside of Mina. MC is using her as a replacement surrogate for wanting to fuck his own mother is the theory I entertain in my head. What kind of fucked up person watches porn of their parents? I don't know if you will consider MC's mother being fucked in flashbacks being considered NTR, considering MC projects his own mother onto Rosalind... it's a heavily grey area.
Given the hints given by multiple characters (Darius's disappearance, Ian's warning, Chuck's warning etc) it wouldn't surprise me if some of the "bad ends" are tied to the MC getting too involved with the Carnations to stay professional.