I share the pain everyone is feeling about that character he really is just a tool to draw out the plot. But in the other hand, we're finally seeing some support characters die off. I mean really, this is a war manga so some people have to die off even if we don't want it. Oh this is just my take on Riboku, but I believe he's just to big of a "fish" for anyone to kill him. His death carries a huge amount of credit that no one will be able to kill him off personally. No matter how much we may wish it, I don't believe Shin will ever kill him.