Rapid

is a Third Generation technique used by Shinra Kusakabe.

Overview
By using the Tora Hishigi Kata, Shinra is able to condense his flames into a single jet blast, as opposed to how his flames normally spread out in every useless direction. This concentrated thrust grants Shinra an exponential boost in speed and allowing him to fly farther and faster while using up less of his fire.

Since kinetic force equals mass multiplied by speed, the increased speed granted by Rapid makes his kicks that much stronger.