My super cool theory: the clover mastermind DOESNT have any powers, he is just a mad genius wit possibly hacking skills (which would explain some things). He will figure out her power by what the sister said to him, and by stalking them and seeing how its clear what Yotsuba is doing needs time travel (e.g. what happened with second place in class guy) (or just by interrogating his brother, which would be more boring... or both).
And then the brother had no connection to the mastermind at first, and only cut off communication between Uichi and Yotsuha because he saw how obsessively motivated she would get by them (not healthy), or he just wanted to have her for himself (psycho). And the reason he let her go from the hospital is because he knew that he could not stop her from escaping since she got time travel powers, and will try to stop her when he learns more about her power (and maybe later on her joins forces with the mastermind to get her back). Or he is just nice (maybe).
And then the climax: the mastermind tries to attack yotsuha, making sure she cant rewind with the watch (restraining her). Also would be funny if she JUST got it fixed or something, but also funny if she couldnt even use it.
Super headcannon fan theory (not like I wasnt just writing fanfiction at this point): And then maybe while caught (and possibly Uichi being killed) she has another mental breakdown and the clover saves her somehow (maybe she breaks it in her madness and then she only has that last chance, 1 day before the attack).
Rate my fanfiction out of 10 😁.
Also PLEASE let Uichi help Yotsuha mentally and with her plans (by his own deduction/will preferably, but not that important).
Also also how did the mastermind find out Yotsuha knows about him? Hacking? Assumption since Yae didnt respond? Stalking? Probably one or more of these.
Rambling is fun