avoids sword strike

Then, Tatemiya, rotating his entire body, whipped his blade to the side in a straight
horizontal sweep. But it seemed like he noticed it after he started the swing...that
Kamijou, his back against the wall, was smiling fearlessly.
(I can do this...!!)
Kamijou crouched down as far as he possibly could.

He knew that if he fled to the side when his opponent brought the sword down, he’d
normally follow up with a horizontal slash. Bringing the sword up again would have
created an additional step.
With his body as low as he could get it, he charged Tatemiya, his face low enough that he
could lick the ground. He didn’t need to think about anything but a horizontal slashing
attack. Even if Tatemiya had tried to unleash a top-to-bottom one, he’d be a beat too late.
If he did that, then Kamijou’s fist would reach him before he could swing his sword
completely.
So Tatemiya Saiji had gone with a directly horizontal sweep, just as Kamijou had
predicted from the beginning.
Kamijou let the sword graze right over his head, and though his heart was in the iron
grip of terror...
“Woh...ohhhhhhhhhhhhhhhhhhh!!” he shouted, clenched his fist, and lunged right into
Tatemiya.

- Toaru Majutsu no Index Volume 7, Chapter 2 Part 7