Looks:- Spoiler:
Almost every Kunai Karasu carries around with him are specialy modified to fit his jutsu. Cut into the grip of each kunai are three evenly spaced minuature holes. The holes are extremely tiny and must be cut perfectly as to not ruin the flight projectory of the Kunai or the effect.
Description: When the Kunai is throne wind flies through the holes producing a peircing sound. By using the Yowakuursu Clan Kekkei Genkai of manipulation of sound the sound that is produced through the holes when its moving is easly used to the advantage of Karasu.
((ex: I throw a Kunai, as its moving through the air the wind goes through the holes producing sound. I can then (using my Genkai or sound manipulation) use the sound created. Amplifing it to hurt the eardrums and etc.))
History:These unique Kunai were shown to Karasu by his father Tousen. His father, and grandfather for that matter, had created these weapons craftly for years. Karasu's father showed Karasu how to craft and use these weapons at an early age. The creation of these weapons is known only to the Yowakusuru clan as it requires their Kekkei Genkai to create perfectly.
To make these you simply do the followong: Choose a Kuni you wish to make. Activate your Kekkei Genkai. Then using the sharp peircing justu of sound and wind you pirece holes into specific parts into the Kunai thus enabling wind to trvel through the weapon producing sound.