Itachi's Crow

This is one of Itachi Uchiha's crows, which had Shisui Uchiha's left eye implanted into it. Now, it seems to follow Naruto Uzumaki as per Itachi's instructions

Background
Before his death, Shisui entrusted his remaining eye to Itachi to protect Konohagakure. Itachi implanted the Sharingan into this crow.

Appearance
The crow looks no different from a normal crow, except for the fact that its left eye bears Shisui's Sharingan.

Itachi Pursuit Arc
During an encounter with Naruto, Itachi asked Naruto what he would do if Sasuke ever attacked the village. Seemingly satisfied with Naruto's answer that he would stop Sasuke and save the village, Itachi stated that he would give Naruto some of his power but hoped that he would never have to use it. Using a genjutsu as a distraction he sent one of his crows inside of Naruto.

Shinobi World War Arc
When Itachi was revived during the Fourth Shinobi World War, the crow emerged from Naruto's mouth during his and Killer B's fight with Itachi and an also revived Nagato and overwrote Kabuto Yakushi's control over Itachi. Itachi later explained that he had set up the crow it so that it would show itself in response to Itachi's Mangekyō Sharingan. Itachi made it so that the genjutsu would give the order "protect Konoha" to whomever was affected by it. Itachi intended this to be used on Sasuke Uchiha, as he anticipated that Sasuke would transplant Itachi's eyes into his own and also feared that he might one day turn on the village.