"...Indeed. Shiki is incapable of causing anything but destruction. And as far as you're concerned, I'm Shiki after all."
"---Shiki?"
"...My Origin is Nothingness. As a result, Shiki, who is possessed of that body, can perceive death. Two years ago--- when she fell into a coma, the outside world was shut off to her. Her vision turned inward toward the nothingness called Ryougi Shiki, and she felt the touch of death.
Shiki floated on the sea known as the spiral of origin for a long, long time. A solitary form in the void of 「 」."
...With an Origin like "Nothingness" the girl would certainly feel compelled to return everything to nothing.
Therefore, she was able to kill all things without exception. Even if the personality of Shiki tried to deny it, her soul itself was oriented toward the death of everything.
"That is Shiki's ability. Just like Asagami Fujino, she has a unique channel that can see things normal humans can't. Eyes that can glimpse the spiral of origin, itself a microcosm of the greater world.
But, I can dive even deeper than she. Or rather... I suppose you could say that I myself am that spiral."