18+ Shichiseiken to Maken no Hime

One day, a clan tried to destroy the "Ancient Sword," but the mission was failed. To prevent the next catastrophe, Sakuya, the strongest boy of the clan, jumps to the next thousand years, but he finds himself in a world of magic. Sakuya, who cannot use magic, is looked down upon as "incompetent"...!

(Source: Kodansha, translated)