"Magic mirror on the wall, who is the strongest of them all?"
"I'd rather have you ask what's the most interesting story we can partake in: for both of us."
Any mirror transmission from between Yukihime and Shirase will always fall down into both rectifying themselves.
"I may have found an interesting piece, but this particular story is empirical."
"What we have to do, or what we should do, it entirely falls as a meddler's move."
"Yeah, I know."
"Whether we do anything or not, the story will progress towards the inevitable."
"Certainly not our battle, despite the despicable movement we're being presented as the greatest adversary."
"It all falls down to what level of involvement we can supply."
Enemy of mankind, so they assume.