Ochikobore Datta Ani ga Jitsu wa Saikyou: Shijou Saikyou no Yuusha wa Tenseishi, Gakuen de Mujikaku ni Musou suru

After a battle to the death with the Demon Lord, Brave Eugene is forcefully transported into the future of the world he had saved. Taking up his new role as "Julius," Eugene is met with disdain and contempt by his family and younger brother Gaias as the powerless loser of the school. However, having obtained the power and knowledge of his previous life, Julius now aims to show everyone what happens when the older brother gets serious!

(Source: K-Manga)