Wind King Slicer

In normal time, Wind King Slicer (風王結界 Fuuou Kekkai) is a mysterious wind that protects the blade it's wrapped around like a scabbard. Through multiple layers of compressed and gyrated wind, it distorts the refraction of light and renders what is inside, the shape of the blade, completely invisible. But it is also a soundless, invisible whirlwind that can act as a protective wall on an area not limited to the sword. The whirlwind it produces enhances the cutting power in a similar fashion to Wind Release: Wind Enhanced Tools. Additionally, it can be used as a distant attack by releasing the compressed wind at once, acting like a hammer made out of wind. This attack is not influenced by Koyoichi's current condition (chakra level or physical strength).

It gives increased accuracy and defense, as it makes it difficult for opponents to parry lunges and thrusts from Koyoichi, for they cannot discern the length or width of the blade. But once the opponent is able to correct the visual disturbance, this technique is not much more than wind around a sword. In other words, it is totally ineffective against an opponent possessing a perception-enhancing dōjutsu, or a powerful resistance (4+/5) to illusions.

Reference

 * 1) Technique Source (Origin)