Kuromaru

is an adult Ninken; a canine companion of a ninja, and the canine companion of Tsume Inuzuka. It hasn't yet been specified whether Kuromaru is a wolf.

Appearence
Kuromaru is an adult canine with a wolfish appearance. As his name suggests, Kuromaru's fur is black. In addition to his wolf-like appearence, Kuromaru is also missing his left ear, along with his right eye--over which he wears an eyepatch. During his first appearence in part I, Kuromaru's size was not unusual for a canine, and perhaps the only canine bigger was Kakashi Hatake's ninken, Bull. Like Akamaru, Kuromaru had experienced a signifigent growth spurt over the time-skip to part II.

Invasion of Konoha arc
Kuromaru, along with Tsume Inuzuka, Hana Inuzuka and the Haimaru Sankyodai, made his first-but-brief appearence during the Invasion of Konoha; as part of Konoha's counter-attack against a battalion of the combined Oto-nin/Suna-nin invading forces.

In his brief first appearence during the Invasion of Konoha, ('Invasion of Konoha arc',) Kuromaru demonstrated the ability to talk.

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.
 * Kuromaru is so-far the only canine companion out of all the Inuzuka clan's Ninken that has exhibited the ability to talk.