@littleeyesofpallas maybe do something about the realms and their names. And how they relate to existing mythology. I have a lot of ideas about Hell.
But I’m sure there is no beast realm. My headcanon is that “the beast realm” is more metaphorical thing referring to humans souls who are are cursed to live as beastmen in outskirts of Soul Society.
My fan fiction idea was that they were human souls in Soul Society who as punishment were forced to reincarnate as living humans. Then when they died, their souls took the form of anthropomorphic animals. But then that practice was outlawed, but their descendants still existed in Soul Society but were shunned. Maybe the wolfmen family are the only ones left? So Genryusai maybe felt bad about the whole practice and so reached out to Komamura to changed the perception of the beastmen.