Sensei might be more of a
Collector than a Homie by then. He seems to be slowly drifting towards the whole:
version of Sensei, every other update.
Recently telling himself he's a Collector and monologuing about seeing the light in Yasu's 'The Art of Drowning' Chapter 4 Event.
Io offered herself to Sensei as well, hence 'Stomachache'.
Difference being that Sensei could be taking Rin's virginity, and it'd all be so unnecessary since Rin is actually into sexual stuff, when she can feel things that is:
Makoto's rape of Sensei was to help quiet the screaming clouds, and because she couldn't just kill herself no matter how many times she had already tried.
I doubt Rin will suddenly become a rapist when she can barely feel at all, but I can see Rin's being similar to Io's, just with blood from different places streaming down her arms and thighs, and Sensei working overtime to justify his actions.
Yasu's could be supernatural with her calling Sensei her doctor, or simply being violated and impregnated by Sensei possessed by Pareidolia as she pisses herself in the middle of the woods, screaming for her god, who isn't around.
It really just comes down to how Sel wants to do it, and any of these girls surviving isn't exactly necessary, considering they'll probably just come back.
I've somewhat touched on how things could be in the future:
Of course, everything could just be A-Okay, and the Dark Route is dark for some other reason.