Thinking about how Suguru was ready to die by Satoru’s hands back then in Shinjuku in 2007…
That would mean that he either already found at least one adult member of his new family or had some sort of agreement with Kon Shiu to take care of miminana on the occasion of his death.
That would also mean that by that time he had already made peace with his life being in Satoru’s hands.
I have to think that, on some level, it was implied that the family would take care of Nanako and Mimiko if anything happened - they were family, after all, and I don’t think there needed to be a spoken agreement
It was probably either Larue or Manami that took them in, since Miguel left, Toshihisa didn’t have much interest in the kids, and Geto wanted to keep the girls away from non-sorcerers.
(my bet is on Larue since he was the most dedicated to Geto and seems to be close with the girls)
But that doesn’t at all diminish OP’s point, because either way Geto would’ve been entirely prepared to accept his death, trusting in his family to take care of his daughters.
