Itachi's Story - Light and Darkness: The Darkness of the Akatsuki Naruto: Shippûden : Season 20 Episode 456

Itachi becomes a rogue ninja and joins the Akatsuki. He is welcomed and introduced by Pain and Orochimaru as the ex-Leaf ANBU and the man who massacred his entire clan. Itachi is paired up with a man named Juzo, and their first job together is to fulfill an assassination request in the Land of Water.