I'm guess Kazu's role in the story is finished. I think didn't know what else to do with Kazu. His character isn't as prominent as other characters. The most we've seen him do is act angry and eat fried chicken, and then his character does a 180 after Yuri's failed suicide attempt with Reiji. Same goes for the grandma who supposedly has dementia.
I find it interesting that in the previous climax, it was Reiji being pulled in all different directions and everyone sinking further into the abyss. Now the story focuses more on the mother's manipulation and how she orchestrated this entire scenario.