Feinting, with the Kakitsubata.
When Shichika crossed through the doorway, intruding upon Uneri’s domain, between his first step and his second step – and his zeroth step when he was immobile, to be precise – he altered his movement speed.
From his zeroth step to this first – in other words, as his rear foot sprung from the tatami, he was soaring, as far as Uneri was concerned. But from the first step into the second, as the front foot sprang to action – Shichika threw the brakes.
The difference between his opening speed and closing speed was unbelievable. Seeing him accelerate, you never expected the coming drop – he slowed down twice as fast in that sense. The effect was marvelous – Uneri, skilled as he was, misjudged the timing of his iainuki.
His opponent hadn’t taken a second step – much less a third.
He motioned for it – but didn’t follow through.
Or he did follow through – but only afterwards.
All of it a single move.
Uneri was sure he had seen Shichika pass through the doorway and all the way in – a misjudgment.
Iainuki has a shortcoming, in that once the blade is drawn, it cannot be stalled midway – unlike the kaleidoscopic footwork displayed by Shichika in the Kakitsubata, its speed cannot be adjusted freely, and can only mount ad infinitum.

Katanagatari Omnibus 1, Page 187