I really like this artist a lot, their artstyle, the uniqueness of the story...
There's a mindbreak-ish feeling about this, but at least she seems happy with her new Master.
...Okay, go back to the last page, and interpret it as if you hadn't read the rest of the story from a god's eye perspective. She doesn't know who he is any more. He erased her memory of it again, and likely a whole lot more if she has no reaction to the man who raised her being killed, likely at her own hands. I get the feeling she's referring to him as master in the sense that he's a wandering medicine seller, not that she has any relation to him whatsoever(that she can remember.
Now it seems you are the one who's imposing your thoughts on the story. I don't see it's mentioned anywhere in the chapter that she got her memories erased, that just sounds like your own interpretation. Rather, it's more apparent she got tamed by Kiyomitsu and completely switched side. As for her not feeling anything when the clan head was killed, that's got some buid-ups previously when he treated her as a whore and clearly disappointed her, both in images and in bed. Also, mind you, this is still a hentai story in the end, so I'd suggest not trying too hard reading into things. :P
IMHO, Kiyomitsu could be classified as either (A) "You're Despicable!", (B) "You Lucky Bastard!", or (C) "Why Not Both?"
I pause to shed a Manly Tear for Kasumi-san's (now former) Master ... but "them's the breaks" in the shadow-coated world of the ninja.
At least there's little likelihood of this being adapted into a *cough-cough* Grade Z movie, produced and/or directed by Godfrey Ho (those who recognize the name would understand).
Oh, a sequel? Nice. After how the last one ended I was certainly interested in seeing how things would go.
Also, a bit of mind-break feel to this one, too. Despite finally laying with her master, the other guy's training had already taken effect and she's...Well, addicted to him now.
It's kind of sad that she was essentially broken down to the point where she thought nothing of assassinating someone she considered family, but alas. At least she seems happy with her new master by that ending.
Knowing what the villan wants in the prequel, this is kind of a bummer. The mind/will breaking is there but it's definitely not as pronounced as it usually is in hentai given the situation. I think if the prequel could have hinted that she would go down this path more then this would be more palatable.