Without reading the other languages, my personal guess is that it's Fuu-chan's inventor dad. I'm guessing she genuinely cares for Yotsuha and is capable of limited time traveling herself. I'm guessing that in the original timeline, Uichi and Yotsuha have a misunderstanding, and Yotsuha hangs herself, seeing Fuu-chan's reaction to seeing somebody hanged. But I'm guessing she'd rather Uichi die and have Yotsuha depressed than whatever the alternative might've been.
Either way, there's also a pretty high chance Fuu-chan was the one who killed the evil mom. It's probably not gonna resolve as easily as simply just talking it out
Either way, there's also a pretty high chance Fuu-chan was the one who killed the evil mom. It's probably not gonna resolve as easily as simply just talking it out