>>853318
OP, what have you done to eliminate the possibility that Miku is simply doing the peace symbol? You know the Japanese (and I think Asians in general) pose with it, right?
I specifically recall in the fictional Magical Girl Anime "Magical Girl Meruru", we can see Meruru posing with a sideways hand-gesture next to her face. I don't watch Magical Girl Anime but I'm quite certain that this is kind of posing is reflective of actual tropes in the genre.
Also, doing an Image Search, I found this:
http://images6.fanpop.com/image/answers/3103000/3103921_1355699848874.29res_500_281.jpg
This is a standard pose for Magical Girls and has nothing to do with Freemasonry. The Japanese are completely apathetic to both Satan and God. If this symbol really is satanic, I'm confident that it's purely coincidental.