"I Will Love You Forever" (お前をずっと愛している, Omae o Zutto Aishiteiru) is chapter 590 of the original Naruto manga.
Summary
With the Summoning: Impure World Reincarnation released, all the reincarnated shinobi began to fade into pillars of light. As the battle between Tobi and Naruto ensues, Naruto charges at him, stating that his opponents were in front of him as Tobi contemplates the fact that Kabuto had seemingly been defeated. Meanwhile, the five Kage struggle to combat Madara, as as he is about to deal another blow with his sword, Madara's Susanoo suddenly dissipates and he is enveloped in a beam of light, causing him to wonder what happened to the summoner. Back at the cave Itachi uses the last of his consciousness to show Sasuke his memories of the Uchiha clan massacre, showing him when he came into possession of Shisui Uchiha's Sharingan, Konoha leadership's decision to move against the Uchiha clan's coup d'etat, his meeting with Tobi and ending with Fugaku and Mikoto's last words to Itachi. With the full truth about the massacre revealed, Itachi told Sasuke that even if Sasuke never forgave him, and no matter what he decided to do from that point on, he would always love him.