She curtly swung down the sword.
In the next instant, Kamijou Touma saw a dimension being severed for the first time in his life.
Its range was a little less than 20 meters.
With a strange noise, something passed through along a line that Kamijou and Acqua had been on just a moment before. Something like a belt or a wall that was only about as wide as Curtana Original expanded. It was white and looked a little like a plastic model before it was colored. That object that looked not entirely complete appeared before Kamijou’s eyes.
[...]
“Did you know that the cross section you get by slicing a 3 dimensional object is 2 dimensional? And slicing a 2 dimensional object creates a 1 dimensional cross section.”
[...]
“Similarly, when a dimension higher than our 3 dimensions is sliced, the cross section appears in this world in a 3 dimensional form. As a result, the ruins of a cross section appears like this.”

Toaru Majutsu no Index vol.18 ch.5 pt.10