Koiruwani is a crocodilian, and the personal summon of Utakata. He is a large, limber, semi-aquatic crocodile. He is first seen during Utakata's battle with Sasori, where he protects Utakata until he is dismissed upon Sasori's apparent death.
Besides the obvious strength and ferocity of a large crocodile, Koiruwani has the ability to coil himself around people, either as an imprisonment or a shield. He can also use a special jutsu which makes the earth before him ripple, striking foes.