So Nishi, after reviving Norihiko, asks him where ranzo and Norihiko tells him that he ran away and Nishi was relieved to hear that and maybe that got under Norihiko's skin and which is why he stabbed him or maybe because Norihiko is not right in the head! I mean he IS trying to break the young master for money as revealed in vol 4 so he's kind of a psycho.
And no I think that's it for him in this volume. Maybe we'll see more of him in vol6 or maybe ranzo will kill him to protect his broski idkidk I really want the latter part to happen lol
This site kind of has the summary for all chapters till chapter 22.5 which is the latest one I think, BUTT it's in Japanese so like translate it using your browser.
https://umi-hotaru.com/magazine/onblue/tourou-no-ori-22-5wa/
After the brothers flee the mansion with lida in vol 4. Nishiura goes inside the apartment and saves Norihiko who like the complete degenerate he is, stabs Nishiura with a knife and flees.
I think Sachiko calls for help and stops the fire, and finds an unconscious Nishimura with a stab wound.
The brothers and lida are at a hospital where lida tells the young master that the doctors found out that he was being raped repeatedly and then he suggests that they could go live with him in Tokyo.
Our cinnamon roll Ranzo suffered from burns and has both hands bandaged and is at his brother's side, all cute and uwu. Thats the end of the volume.