Hey, it's me again. Out of the two oni sisters, who do you think I should incapacitate first?
If you get into the making out stance with Mizuko (the blue one), she can't use her butt-hypnosis on you, making her pretty easy. Himika is also limited in what you can do while you are in stance with her sister.
So one of the easiest versions of the boss sisters: Make out with Mizuko until she is down, then hit Himika in the ass.
Additional note: Powered up Himika's loss scene is quite possibly my favorite loss in the game. Possibly one of Sofia's beats it. (Note the username here)