Itachi's Crow

Outwardly it is just a black crow. What sets it apart is hidden within: the left eye of Shisui Uchiha, sealed inside the bird for protection. Itachi also mirrors its form when he dispatches a crow clone in his place.

The bird proves entirely compliant. When Shisui merged his eye into it, the crow offered no resistance, gave a single nod, and took wing. From then on it trailed Itachi silently from far above, a constant unseen guardian that shadowed him even as he abandoned the village.

Shisui had hoped to end the Uchiha's brewing coup peacefully by casting Kotoamatsukami, but Danzō Shimura seized his right Mangekyō first. Rather than let his left eye be stolen too, Shisui tore it out and pressed it on his closest friend Itachi, begging him to use it in Konoha's defense; the eye was then hidden inside a crow. Years later, during the pursuit of Itachi, a clone in crow form approaches Naruto and probes him about Sasuke. After a failed strike and a genjutsu of swirling crows, the clone asks how Naruto would answer if Sasuke ever turned on the village. Naruto swears to shield Konoha without taking Sasuke's life, and the pleased clone sends one crow diving down his throat, saying it hopes the bird's power is never called upon.

Itachi later lays bare the design: Shisui's eye had been set to unleash Kotoamatsukami on whoever came to hold Itachi's own Mangekyō, forcing that person to defend Konoha. He assumed Sasuke would one day take his eyes to stave off the blindness the Mangekyō brings, and that if Sasuke then attacked, Naruto would face him, making Naruto both the perfect carrier and the perfect deliverer. The plan misfires during the war. Revived by Kabuto through the Impure World Reincarnation and forced to battle Naruto and Killer B, Itachi uses his Mangekyō, which triggers the crow inside Naruto. It bursts from his mouth and turns Kotoamatsukami on Itachi, and the command to guard Konoha overrides Kabuto's puppetry, freeing Itachi to join Naruto and B against Nagato. Since the eye can only cast the technique once a decade, spending it early wrecks the original scheme, so Itachi burns the crow away with Amaterasu to keep Shisui's eye from the wrong hands.