Yukina had been prepared, and as such she took the initiative. Swinging Sekkarou, she managed to effortlessly tear through the clones in her area simply out of a virtue of compatibility - the clones were created through "supernatural" means - means of magic. So long as they were magic or supernatural, Sekkarou was absolute defeat for them - the clones of magic could not possibly survive that which negates all magic, all abnormalities, short of the supernatural means of the divines; the hierarchy of those who created the world. 

Slicing her way through, Yukina searched for the source of the clones, hoping that by defeating the original the clones would all simultaneously disappear.