don't tell me he's uichi son from future or from another dimension
I'm convinced it's gonna be future Uichi trying to murk himself so Yatsuba lives.So it's someone who hates Uchi but loves Yatsuba. Probably something to do with her suffering due to trying to save him.
She's told her brother about the watch, though. It was part of what got her the agreement to live next door to Uichi. The mastermind was (seemingly) surprised to hear about the clover watch when Yotsuha was trying to use it previously, and has been reactionary to Yotsuha derailing the plans.Don't hurt Yotsuha eh?
That's a nice theory Yotsuha, if it's true then maybe the mastermind is looking out for her... like a brother.
If that phone starts ringing someone pick it up because I have called it.