1. Fair enough
2. + 3. Painfully realizing it is in vain leads her to what? Become part of it herself? Infiltrate? I can see that being a thing where Rin tries to infiltrate trying to do as little sexual stuff as possible but at the same time remain her "cover". I havent seen this set up in any way by the game, gonna be honest. But I see this could be a thing.
I can see this progressing like that, but again, I do not see this set up this way. And Von was talking about starting NTR at Ch. 3, so its really hard for me to see how this is being pulled off.
Plus, would a smart FMC really think its such a great idea to put her own body at risk just to get what she wants?
I know of a few games doing stuff like this, but in most cases the girls were kind of stupid. The only one I can think of that is doing it somewhat passably is
Falling Undercover: Nox Syndicate. Even that one though Im starting to loose a bit of interest cause its too much "well you gotta play along now, its for the good of your lover". Its heavily cliched and it leaves out smarter alternative options. Plus, the entire world was created to set up for this scenario. In the case of Aperature it doesnt seem that way for me so far. It might be possible in this world, but the world wasnt specifically designed with that scenario in mind I feel.
My A-Rank Witch is also doing something along those lines in some paths. Going for the "I have a grand goal and I will do stuff to achieve it cause I have no other choice". But again, the world is set up very much explicitly for this. Plus even there they are skirting the line of the believable. The more you have the character go for stuff like this and entertain these sexual acts - even if it is just an act - the more you will sacrifice the integrity the players see in them.
A few things regarding this.
1. First of all we would eliminate the "she heavily dislikes or hates the villain (Daizo)" with this angle. It is an important element in a NTR or corruption story for
some people (not for everyone).
2. A setup like you describe it would take VERY long until there is even some sexual action or scenes going on. The question here is how long can you go until people become disinterested or are dissatisfied by that. Especially if the corruption arc has very little of that either.
I see where you are going with the idea. I just don't know if Von has planned it this way, if people can stay hooked (me included) and it eliminates a few elements that people like about NTR / corruption stories.