Kazega (風牙 Wind Fang) is the name of Shiro's Zanpakutō. It's sealed state is unknown.
Shikai: Being a constant release weapon, Kazega is always in Shikai, and takes a form similar to what was once Ichigo's Zangetsu, an elegant cleaver-like weapon. It is black and white much like the aforementioned weapon, but it has an unusual cut at the tip of the blade. The hilt of the blade is surrounded by two circular blades that seemingly function to block attacks on his arm.
Shikai Special Ability: Kazega's Shikai Special Ability revolves around the manipulation of wind, the same as his previous ability, however, the influence increases. Shiro can now see the flow of the wind, and can change it's flow to alter an opponents own wind based techniques, stating that he fully controls the wind and any wind based assaults on him are useless. Besides that, his Shikai has shown to channel, manipulate and warp wind around him by slicing with the blades. He has shown to increase the speed of the wind currents allowing him to turn pure air into his weapon. Along with the wind-control, he has shown to gain increased speed by once again- using the wind to push him around.
Artwork © *Zanpakuto-leader
Shiro MorimotoBleach © Tite Kubo