I spent a lot of Flame of Recca going, “Man, I would be enjoying this fight scene so much more if Nobuyuki Anzai had not spilled his sexual hang-ups all over it.” Now I know what happens when he doesn’t spill his sexual hang-ups all over things! He makes manga that is kind of perfunctory, with characters he doesn’t really seem to care about. Okay, Anzai, you can have your sexual predators and dominatrices back.
(Not the pedophiles or the thing with the peeing, though. I’m drawing a line there.)
For me the main value of this manga is the knowledge that (spoilers for chapter 107, plus the end of Flame of Recca) Joker survived falling into a black hole. I like Joker, all right? I’m easily manipulated by this character type. For Joker’s sake, I am willing to accept that the only negative effect of falling into a black hole is amnesia.
It’s not spelled out or anything, but given that Nanashi has Joker’s hair and fang, hides his eyes like Joker, is wearing Joker’s bracelet, and is heavily implied to be from another world, I’m going to assume that the reason we never got into his backstory is that we’re supposed to have figured out that he’s Joker.
(And I just googled and apparently, in the anime it’s made explicit that Nanashi had been stabbed in the stomach, same as Joker.)