To give Naruto a chance against Madara, Obito might've inadvertently erased him from existence. Until he finds a way to bring Naruto back, he'll have to deal with sharing a body with his younger self while the other remains oblivious to his existence. Time travel/ Parallel to Iryo-nin Kasa

A flap from a butterfly could create a maelstrom, a single death could bring unfathomable chaos. Orochimaru dies long before his machinations in the elemental nations and the cause? His very own student. Nawaki Senju.