Senketsu

The blade, Senketsu (潜血; Literally meaning "Occult Blood") is one of the two spirit weapons wielded by Yoshida Uchiha's Susanoo. This blade, wielded in his Susanoo's left hand, is a sword/spear with a reddish-white hue and an eye located at the hilt. The blade usually causes massive shockwaves from the sheer speed and strength at which Yoshida's Susanoo swings it. It can also be infused with Yoshida's Blaze Release to increased the damage dealt with every hit. Senketsu, along with its partner, also utilize Yoshida's concept of Flow.