What I want to know is, did the charm straight up kill off the original?
Like, clearly there was originally one girl. She was split up, and now the pieces have her memories.
But, like, that's not compatible. If the charm edited history to make 2 new families/histories for them, then they should all remember there being 2 girls.
But if it split them after she finished her summer with Yuu, then both girls and their families would have gaping holes in their history before that point.
Anyway it seems like fun.