Thank you for bringing this. I understand if you don't continue it, but I, for one, actually find this to be very interesting. Smut yes, but an intriguing story so far.
His brother seems like a cool guy but the tone this manga has taken tells me that stupid plot twists will await the future, like his brother suddenly deciding he resents being a bastard and trying to kill him only to get executed or something. Prostitute will probably end up killing herself, maybe take the entire brothel with her.
The story is more interesting in context of a historical period drama rather than smut.
The sex and gore is just to draw attention, but their conflict is about social structure change in Japan's Meiji period modernization
where era of the warrior class is fading away and people who are struggling to accept (or reject) that fact.
MC & FMC end up fighting on different sides, MC hooks up with another woman, MC and the other woman make love, FMC kills the other woman, and MC and FMC make love and marry. The End. What makes it infuriating is the other woman is way more interesting, and MC ends up having sex with her and then IMMEDIATELY has sex with FMC after she kills the other woman. Like, we are talking within the same hour here. Just makes MC the absolute worst pile of crap ever.