I think this might be a bug and because of my carelessness when saving the game, I have to redo 3 hours. That's on me. But when I go one on one with Onyeka (the berserker's questline) in floor 7, and let her go after the win, the screen turns black (by the way the first thing I do in floor 7 is fight her). I can still hear the sound of interaction and open the menu though. I fixed this by teleport back and forth but Hana and Gouki are no where to be found in my party. When I go to the arena for the first time, 2 of them still there on the dialogue box, but I'm all alone in the party screen. Can you check it out please?
Update: I kinda fixed the problem of Hana and Gouki missing now by going back to Asari and fight one one with the monster in the inn. However, it's still a roundabout way. Personally, I don't find this too annoying, but you should still look into it.