I actually only bought this book because I needed to get rid of a coupon. Granted it was worth it. I liked it's gritty artwork and story.
For me it was clear early on that Hanbei's power doesn't just seem to be undying/immortal but also regeneration. On the prior page his upper body was almost split down the middle and now all he has is a scar on his forehead. Granted, I get how Hanbei thinks he is immortal (even though he clearly ages) but why does he think he is infected? What makes him think that?
And since this is the same Hanbei that we see in Sekiro, I wondered whether the huge monkey in the forest is the same as in the game, but I think it is not. Apparently it is some being called Yamahito, who could be neither monkey nor human because of his past and he can't become a monkey. However, he must be able to regenerate as he survived a stab into the stomach from the back. And because Yamahito has red eyes, Hanbei can tell that he has "the curse of immortality" ... hm, a tad odd, but I was sure there would be some sort of explanation. Well, there wasn't.
And I knew that the centipede from before was special. Apparently this water here makes them this way. However, how would an insect be able to repair its host like that? And holy shit, is that thing huge. How did that centipede still fit inside Hanbei without him noticing something is inside him?
And to be honest, for a short moment I thought Hanbei would be the old man in the temple carving the statues from Sekiro. But that old man is already there and he has an arm missing, something that wouldn't happen with Hanbei.
That ending was odd and I assume it is supposed to tie in with the game as that is clearly the game's protagonist and so he "trains" with Hanbei. But what that bonus story was about I have no idea.