Minor detail about Rin's route that I don't get...

[kimono]

Obviously, spoilers.

It's about the questions you say to her in the last decision, the "If you found something like that, then what?"
In some places (ej Tvtropes) they put this question as something really shocking to Rin and what makes her opinion change (and leave the exposition). Okay that's fine, but why that happens? I mean, what does Rin see in that question that changes her behaviour so much? Especially considering that everything Hisao tells her aparently have little effect in her and continues to "change" to do her exposition.

What are your thoughts about this? I know it's a minor thing, but it has been bugging me off, considering that everyone put it as an armor-piercing question and I never thought really about it. Makes me feel kind of stupid

[Mirage_GSM]

Well, the two options are:
#"But aren't you happy people are interested in your paintings?" and
#"But if you found someone like that, then what?"

The main difference between the two options here is that in the first one Hisao shows that he doesn't understand Rin's feelings at all. He still thinks that Rin is interested in fame and doesn't understand that she is distressed by having to explain stuff.

In the second answer he at least implies that he might be able to understand her feelings a little bit.
It is probably nothing in that line that makes her leave. I think it's more the other way around: Leaving is her default decision and in the other path Hisao pressures her to go back in.

Also, in the second path Hisao asks her some profound questions that she probably wants to think about.

With all that, keep in mind that it is not only the one line in the choice that influences her actions but the whole conversation in the branch that follows.

[kimono]

mm... yes, you're right. It makes sense. Your interpretation looks correct.

I always thought (and I guess it's the general opinion) that what truly makes her Rin change is how Nomiya is (also) angry with her and the next conversation she has with Hisao, but since tvtropes put this answer as a big deal or game breakes it made me doubt a bit.

This route sure needs one or two replays to grasp everything (and for enjoy it too), damn...

[Mirage_GSM]

Well, TVtropes is not my go-to sight for insightful interpretations of literature...

Generally you shouldn't think of any single line in the choice menu of a VN as THE line that changes how the characters feel about life, the universe and everything.

It's relatively easy if a line directly influences the actions of the prtagonist. An example would be Shizune's route where you decide whether or not to "comfort" Misha or Hanako's route where you decide whether or not to give her some personal space.

On the other end of the spectrum there's the kind of choice that is completely inconsequential - like almost all other choices on Rin's route - there only to confuse the reader.

In the case you mentioned - or the scene in Emi's route in her kitchen, or ALL OF Lilly's route - the choice is simply there to test the reader; to see whether or not they understood some key part of the female lead. If the reader shows that understanding, the story will continue on to the good end, if not it will continue to the bad end. It's not neccessarily that single line that will change the outcome; it's that you have proven that the protagonist has understood some important detail and will be able to steer the story to the good end from there on.