William and Knight Leader had jumped straight forward from the large trees. They seemed to slide through the air as their display of strength twisted gravity and their bodies and swords relentlessly clashed at the halfway point.
[…]
The energy they had used to drive themselves forward was completely lost in the first strike and the mercenary and the knight began to fall directly downward. However, a free fall was no threat to those two. They continued to swing their swords in close quarters.
Their swords bit into each other complexly.
In a midair battle with no footholds, one could not properly use one’s own weight to swing one’s sword. Instead, William and Knight Leader used the energy gained from stopping their opponent’s blows to rotate their body around and return the powerful blow from many different angles. This repeated again and again and again and again.

Toaru Majutsu no Index vol.18 ch.5 pt.3