Kuromaru

is the canine companion of Tsume Inuzuka. Kuromaru has a wolfish appearance and is missing his left ear and right eye. As his name suggests, his fur is black. So-far, out of all the Inuzuka ninken, Kuromaru alone has exhibited the ability to talk. It hasn't yet been specified whether Kuromaru is a wolf.

Invasion of Konoha arc
Kuromaru, along with Haimaru Sankyodai, first appeared with their human companions during the Invasion of Konoha, repelling the Oto-nin and Suna-nin.

Invasion of Pain arc
Kuromaru appeared again during the invasion of Pain. As Pain's Preta path prepared to dispose of the previous Animal path, Kuromaru and Tsume attacked it with Dual Piercing Fang. The Preta path used the Animal path as a shield and avoided the attack. Kiba and Akamaru joined them in the battle, but the Preta path was summoned away before Pain crushed the village.

Trivia

 * The 'Kuro' in Kuromaru's name means the color 'black', and 'maru' meaning 'perfection' or 'full circle' is a common suffix for Japanese male names.
 * Kuromaru is the largest canine companion seen out of all the Inuzuka ninken.