Hazure Skill "Omoidasu" de Kioku wo Torimodoshita Daikenja ~Gendai Chishiki to Saikyou Mahou no Yuugou de, Isekai wo Musou suru~

Kengo Kurono was summoned from modern Japan to another world as one of several prospective Heroes. While the other summoned Heroes receive spectacular abilities, Kengo is saddled with an F-rank skill called [Recall]. Deemed completely worthless, he's cast out of the royal palace and eventually used as disposable bait in a monster-infested wilderness. But just as Kengo is certain he's about to die, [Recall] finally activates. And he remembers something impossible. Before his life in modern Japan, Kengo had already lived once before in this very world. A thousand years ago, he was the legendary Great Sage, one of the most powerful magicians who ever lived. With those memories come his former knowledge, experience and devastating magic. The supposedly useless Hero immediately annihilates the monsters surrounding him with a meteor spell and begins reclaiming the abilities of his previous incarnation. But Kengo isn't the only person carrying memories from a thousand years ago. His [Recall] skill awakens the past lives of others as well, including a beastkin girl who once existed as a divine beast, an elf descended from the Sword God who rivaled him, and a young dwarf carrying memories connected to his former disciple. Now possessing both modern Japanese knowledge and the magical wisdom of the world's greatest ancient sage, Kengo sets out with his unusual companions to uncover what happened during the thousand years he was gone. His first order of business, however, is considerably more personal: dealing with the empire that branded him useless and tried to have him killed. And behind it all, demons Kengo remembers fighting a millennium ago have begun moving once again. A second-life-within-a-second-life fantasy about a discarded Hero discovering that his supposedly worthless skill contains the memories and power of the strongest Great Sage in history.