A 30-year-old Japanese salaryman named Minoru Kido dies in a traffic accident, his life ending without leaving any significant mark on the world. As he passes, he wishes for a second chance to live a long and meaningful existence. His wish is granted, and he is reincarnated as an elf named Liese Klein in a fantasy world where elves possess lifespans of up to one thousand years.

Determined not to waste this opportunity, Liese vows to spend his new life honing his magical abilities and leaving undeniable proof of his existence. He dedicates his early years to intense study and training within his elven village. By the age of 20, he has already mastered all forms of healing magic natural to elves. By 30, he has learned every attribute of offensive and defensive magic. Finally, by the time he reaches 100 years old, he has deciphered all known ancient magic formulas, effectively mastering every form of magic in his world.

With no magical challenges left and approximately 900 years remaining in his lifespan, Liese decides to leave his home and journey out into the wider world. However, before he can depart, the elder of his elven clan imposes a final trial to test the true extent of his power. After successfully proving his strength, Liese begins his centuries-long adventure.

The story follows Liese as he travels across the land, his immense power and long life allowing him to witness and shape history. During his journey, he encounters a nameless human girl whom he saves and names Minori. He also takes on an aspiring adventurer named Jin as his apprentice. As the centuries pass, Liese inadvertently influences major events, such as aiding a fledgling hero, having a country founded in his name, and being worshipped as the founder of modern magic. His long journey is driven by the goal of creating a lasting legend, with rumors of the Demon Lord's resurrection eventually providing a clear objective for his power.