Kaettekita Tensai Kensei: Maryoku Zero no Ochikobore na no ni Jitsu wa Saikyou

A century ago, Agito Yatsurugi and his comrades saved humanity by slaying the six dragons that invaded Earth through magical gates. As he lay dying, he learned the dragons would return in 100 years to awaken the dragon god and end the world. Granted a second chance, Agito awakens in the body of Agito Mitsurugi, a powerless F-rank student at a magic academy. With time running out, he must rally new allies--some tied to his past--to face the reborn dragons and stop the coming apocalypse once and for all.(Source: WEBTOON)