No mention of Shaku at all, in the ending wrap up. No idea what becomes of her. Did she pass away around the same time as Shinsuke, or live longer as something not quite human? Feels odd to me, and leaves me a little unsatisfied.
Figured I should mention that a modern descendant of Shinsuke & Shakuyaku, Hinode Kazamatsuri, is featured in Chapters 9, 17, 18, and 21 of Mizukami's anthology: https://mangadex.org/title/79/mizukami-satoshi-tanpenshuu.
@Selimay I'm preety sure the woman he met who talked about her still ageing despite being a modified human was Shaku. I think it's implied that her life span was longer than a regular human but she still got old eventually
@psydynamite I think this was a fitting end to Shinsuke's arc. He's no longer the naive innocent boy he was before so he decided to murder Yazen. But unlike his revenge driven days it didn't come from a place of hatred, but instead it was a purely logical decision since if he wants to keep the people who he loves safe Yazen is a threat to that with his potentially world ending experiments (looking at you Senya). But since after all the peace that he's created it's fitting that he both suceeded and failed in the end in that Yazen managed to survive but he's unable to continue to experiments even if Shinsuke intended to kill him.
Also can I just say that's badass as fuck. He did a 2 vs 1 match against opponents who were both several times stronger than him , won the match and had them fleeing for their lives barely hanging on to life. Shinsuke's by far my favourite character in the manga so I'm glad he was able to be badass just one last time.