I am canonblind except what I've learned through osmosis (my dude your canon has a lot going on????) BUT I suspect these characters would have interesting CR! John is an immortal wizard who possibly ended the world, possibly created magic in doing so, and who has a complicated relationship with grief and self and morality. He has declared himself God and he's extremely powerful and difficult to faze with fucked-up content. idk where to go with this yet but I look forward to them being in each other's orbits - John is friends with Sayo and will be teaching her magic.