A++++ explaining. (Also nice icon what manga is that)
Thanks, I have a lot of time to think about this kind of thing, but I definitely got something wrong, most likely about "Izuru" learning about the rape from Satsuki, this scene is a little ambiguous, when she talks about the promise to take care of Anna you see a letter and Satsuki writes this letter, later Satsuki kills herself and says to "Izuru" to take care of Anna and as she falls she thinks about how she hates not being able to do anything in return for Anna kindness, so I suspect in the future of the second timeline she also kills herself and leaves that letter to "Izuru" telling her about the rape and asking for her to take care of Anna and that's the reason she made "Izuru" remember about the rape here, because she's the one who told her about it in the future, or that was just a coincidence and this scene is just "Izuru" thinking about how Satsuki made she remember about the rape that would happen that day and that letter was written by another person.
My avatar is from a one-shot Ratana is making, you can find the original here.
I think the letter thing before the trip is just Satsuki's way of talking to Izuru she just explained her plan and the reason behind it [being a psychic and all] because she doesn't really talk until, you know…the jump. In chapter10, since Ninose is a psychic, she sensed/saw the danger that was going to befall on Anna that day during their presentation and ran to Izuru when Anna and Kazuya were nowhere to be found to let her know, Izuru, on the other hand instantly remembered the day Anna got broken in Izuru's world after seeing Ninose's reaction (good thing she was able to stop it by the way :P). And after sacrificing herself Ninose jumped to her death because it was too much for her…*why?!?! Oh why?! she was my favorite X{ *
Anyway, that's how I understand everything so far...