First off, kudos to WareMete, for having the Astronomy Club, despite having only one astronomy-obsessed member and a primary mission that has nothing to do with astronomy, actually putting in the work that’s necessary for the upcoming festival. They also want to do things the right way, without shortcuts, meaning baking all the goodies and building the intricate planetarium device themselves.
Granted, they don’t quite get the personnel distribution quite right the first time, as Kenny is more interested in Sou’s booby mag than working on the device, while Yui seems only marginally interested in baking with the experienced Kaori and the eager newbie Airi.
After a test batch, Yui takes Kaori aside and asks her point-blank: “Do you have feelings for Akiyama?”; Kaori’s reaction is a sufficiently clear answer, though she lies and maintains they’re just old friends, then starts creating opportunities for Yui to be alone with Sou – putting Yui’s assumed feelings for Sou above her own.
While showing off the fruits of their labor, Sou points out a basic scientific fact that I for one only rarely consider while looking up at the night sky: that every time you look up at the stars, you’re travelling back in time…and not just to your parents’ high school prom, mind you—but to an ancient time before human civilization…or even humans period.
Seeing the stars jogs a distant memory of Yui’s, and I think we learn that for her, living in this world is for her what looking up at the stars is for everyone else, though not on quite the same epochal scale: she’s traveled back in time. I say this because the man in the white coat admiring the Summer night sky in Yui’s memory looks suspiciously like an aged, grizzled Sou. And as Kaori suspected was the case with the present Sou, Yui has the feeling this future person means (or will mean?) a great deal to her. Kaori hears that bit on the other side of the door and is further dejected.
The importance Sou has for her is further exhibited when he gently wakes her up and, with a dream of that other time still fresh in her mind, she puts her hand on his face before snapping out of it. It’s something one would do if you suddenly found yourself before a loved one in the prime of their youth, before that face was weathered by the burdens of life and tragedy; in other words, when their skin was almost as silky as Jennifer’s.
If the stars of Sou’s planetarium or other stimuli continue to jog her memories, and more details from that future come to light, Yui (and our) understanding of those feelings will grow, as will the amount of information she’s presently concealing, though Sou got a little bit out of her. In any case, judging from her hospital-like attire, it’s reasonable to conclude (*gulp*) that Yui is the girl in the tube, and Sou sent her back to save Kaori…even though Yui loves him too.
The titular Lost Future, therefore, could be the future with Kaori Sou lost when she was hit by a bus (or some other misfortune), or the future Yui lost by traveling back in time, leaving Old Sou behind. There’s a nice symmetry between Yui helping Sou save Kaori in the future and Kaori yielding Sou to Yui in the present.
Temporal Love Triangle FTW, Baby.