soft deconfirmed since rentarou is still with his harem sans nano in the synchronised world, but i thought it would be funny if its revealed alt universe nano lives in a world where god didn't get distracted by castle in the sky, therefore never causing rentarou's 100 rejections nor his fate of being with 100 girlfriends which causes nano to never reexamine her callousness. rentarou locks in and travels through time and space to put castle in the sky on tv at the exact moment, thus ensuring that nano is never given reason to cry but also causing his 100 rejections to happen in the first place
Holy shit ur right, I was thinking if we could deduce the "point" of separation,so I was going "since nano is a 1st year in high school she is 15-16, the other nano said she came from 20 years in the future of the other universe, so she is 35, if she met rentarou, and soulmates who can't get together die because they used all their luck to meet each other, could other-Nano had lived to 35?" and doing this path to see if maybe she didn't meet rentarou, but if the Rentarou family still exists in the sync'd world (and look who the authors use to show it,
Shizuka, Matsuri, Kishika, Mimimi and Eira, they are all from different years from Matsuri being from middle-school and to Eira who is from Uni) the family is still intact apart from Nano.
So the God still did the mistake with Rentarou's soul and the family forms, so other-Rentarou still went through the night to find 2 clovers for other-Hakari and other-Karane, the other dimension really is either a world where by pure chance she never, in the 3 years they were together in school, looked eye-to-eye with other rentarou and the "death by not meeting the soulmate" is just really slow or she wasn't one of the soulmates of that Rentarou.
This fits with what God said to Rentarou at the start, that he will meet the 100 soulmates while
HE is in highschool so other-Nano could be our Rentarou's soulmate while not being the other dimension's. if she is a soulmate her fate was to do all of this and meet rentarou at 35 while he is a highschooler
This arc could either end with the other Nano coming back even though she said she wouldn't, locking eyes with rentarou, sync'ing her memories with our Nano and reverting everything to stay as a GF,
other-Rentarou from a 3rd dimension comes to save the main one,
or our Nano fixing everything like another commenter said
the synchronization goes through and Nano spends the next 20 years creating time travel. Then instead of going back and fixing her timeline, she goes back to the past of the Superior Nano timeline and syncs it with the "main" world, so Alt Nano falls in love with Alt Rentaro and never starts the dimension hopping nonsense (which retroactively means the main timeline was never touched and everything goes back to normal).
And the moral will be that "main" Nano ended up accomplishing more than the Efficent Nano, since emotions pushed her further.