Nishuume Cheat no Tensei Madoushi: Saikyou ga 1000-nengo ni Tensei shitara, Jinsei Yoyuu sugimashita

Having become overwhelming strong, a mage was bored with his life and decided to reincarnate in another era about 1000 years later. But after reincarnation, the mage now known as Kurt saw a world where magic had declined, and the mages of the era are overall much weaker than those of 1000 years ago. It also seems that Kurt is being looked down upon for his Gold Magic as it is called Defective Magic Power in this era. In order to investigate the mysterious decline of magic in this era, Kurt enrolled in the Magic Academy at the Royal Capital and showed his extraordinary talent where he would become unparalleled in this second life of his too!?

(Source: Shousetsuka ni Narou, translated)