Responses
The Japanese release have story from their grandpa x father.
and this (current manga you're reading) release focus on the brothers sides.
The main focus for both story is they're in a family of cult, worshipping demon/devil.
The younger brother (mio) doesn't really go with the cult/their family teaching (so he kinda end up being a yakuza). Meanwhile his brother (Sekai) is the current leader of their cult.
Is this related to some other story? It feels like it should know who they are but I don't understand a single thing that happend