Yuukyuu no Gusha Asley no, Kenja no Susume

Expelled from the Magic Academy in his youth and mocked by his peers, Asley seemed destined for a life of insignificance. However, a chance discovery of a miraculous elixir granted him an immortal body. Driven by a desire to prove his detractors wrong, he devoted himself to researching magic and crafting artifacts entirely distinct from the academy's orthodox teachings. Consumed by his work, five thousand years slipped away unnoticed, transforming the once-disgraced dropout into an ancient master of magic. Having long since lost his original purpose, Asley sets out alongside his familiar, Pochi, to witness how the world has changed over the millennia. Along the way, he assists numerous people, but a series of unexpected events ultimately leads him back to the very Magic Academy that once cast him aside. Now trapped in the body of a youth yet carrying the knowledge of five thousand years, Asley must navigate this strange new chapter and discover how to truly live his second life.