Bull

Bull is the largest summon in Kakashi's ninken pack. He has dark fur and wears a spiked collar. He also wears the standard outfit of Kakashi's ninken which consists of a blue vest with the heno-heno-moheji seal and a Konoha forehead protector worn on his left front leg.

In the anime, after they made a contract with Kakashi, Bull and the other ninken aided him to search the abducted Rin Nohara by the Kirigakure shinobi and acted as a diversion in order to allow them to flee. They also helped searching for the fleeing Orochimaru.