I must say, when I've started reading this manga, I was kinda worried it was gonna show a lot of gratuitous sexual violence, but I'm pleased to see both Mie and Iku explored much more. A terrible fate binds both of them, as obviously dictated by times and customs.
I'm also quite pleased to see not only darkness, but also "light" being added to Irako. Now it's all less black-and-white, even though the story still seems to push Gennosuke as the "good guy" against Irako. Since Kozan seems consciously furious, maybe that's how all this mess happens?
Irako kills Kogan in self-defense, thus dismantling the house/school or at the very least burying his chances of becoming a leader. Then Gennosuke, maybe not knowing the reasons for it, ends up fighting against Iraku and either wins (losing his arm though) or loses (while also crippling Irako). And then Gennosuke takes over the school and marries Mie, while Iraku leaves with Iku. That's how I imagine it resolving at the very least.
Also, did Iraku's mom just die? Those last panels look very ominous.