Sure looks like it. And if it is, by god it's awesome. Well it's awesome either way but I think it's been quite proven by now that there is no limit to awesomeness.
It has to be. Shirai is doing Chun Li's forward jump kick attack, and Misaka is clearly Sakura (red armbands, white bandana, shit-eating grin, underwear hidden by shorts/bloomers).
Can't figure out what Index is supposed to be, though.