Not sure who's between Okuu and Miko

Looks like Nue to me. At least looking at her wings.

Likely Hijiri. You can see that, starting from Remi, their order perfectly lines up with mainline releases, and they're all stage 6 bosses of their respective game.

Valentine322 said:

Likely Hijiri. You can see that, starting from Remi, their order perfectly lines up with mainline releases, and they're all stage 6 bosses of their respective game.

That does make sense logically. I'll add her