Mouth
Naraku did not leave all of Kanna's forming to her discretion. He required that she have a mouth, for all his servants must speak, and the first word is master.
Kanna, of course, duly obeyed. Her mouth formed as a thin slit in her face, colorless, without whimsy or aesthetic flair, and able to give off a thin, toneless voice.
The very first thing Kagura did upon her creation was spit. She spat until she spat blood as well, and stained her lips with it. Naked, she kicked the lumps of spare flesh that had not been used in her body, and with foam on her mouth spoke her first word.
Why?
And when Naraku took her by the hair to discipline her, Kanna knelt in her wake, in her blood and spit, trails of color creeping up her dress the way a plant draws up water. She dipped a finger in the blood, and outlined her own lips with it, but in the time it took to turn her mirror on herself and inspect the results, all traces of the blood were gone.
That is the other nature of the mouth. It hungers. It consumes.
Not knowing the nature of Kagura's body, Kanna wondered if unlike herself, she ate, and if so, what? Would that ravenous mouth devour plate after plate of fish and rice like a human's would? Would she suck the blood of the living like a spider? Would she steal out in the night, and take what she needed from the bodies of others? What force kept the bright crimson on those lips, vivid as blood, redder than the mouth of any human?
Since the mouth also digests, she would try to catch Kagura's exhalations, analyzing for the scent of fish, of blood, of anything that might have caught between her teeth and rotted. Her breath did carry a scent, but one that Kanna could never place, one that didn't quite fit into the world as she knew it. It reminded her almost of smoke--not as if she had been sitting by a fire or smoking a pipe, but as if her body itself was on fire, and the scent was not of the flame but of her body's kindling slowly dissipating with every wisp of breath.