A mage who had grown bored with his own overwhelming strength decides to end his first life and reincarnate one thousand years into the future. He hopes that in a new era, he will finally find challenges worthy of his power. However, upon being reborn as a boy named Kurt, he discovers that the world has changed in an unexpected way. Rather than advancing, magical civilization has drastically declined. The knowledge and techniques that were once common a millennium ago have been lost, and the mages of this era are far weaker than those from his original time.

Kurt retains all the memories and immense magical power from his previous life. His magic manifests as a brilliant golden color, but in this age, golden magic is mistakenly perceived as a defective or low-grade ability. Misunderstood and underestimated by those around him, Kurt remains unfazed, knowing the true value of his power. He encounters a girl named Lala, who encourages him to enroll in the magic academy in the royal capital. Seeking to understand how magic has fallen so far and perhaps find some entertainment in his second life, Kurt agrees and enters the academy.

At the academy, Kurt quickly proves that his so-called defective magic is actually the most powerful and refined magic in existence. His abilities far exceed those of both his peers and his instructors, and he begins to overturn the common sense of the era. He makes new friends and faces various foes, all while investigating the mysterious decline of magical civilization. His second life, which he hoped would be less boring than his first, becomes filled with new challenges and adventures as the strongest mage navigates a world that can no longer fully comprehend the heights of power he represents. The story follows Kurt as he balances his life as a student, his growing relationships, and his search for the truth behind the world's magical regression.