Saijaku-shoku ga Zense no Chishiki de Sekai Saikyou - Ore dake Level Genkai ga nai no de Mugen ni Tsuyoku naru Musou Life

The strongest wizard, Roy, is reincarnated into the future as a young boy, Yuug. However, magic has declined since then, and wizards are considered the weakest class. With the knowledge of magic from his past life and his extreme-level abilities, Yuug embarks on his second life's adventure.