Eiyuu to Kenja no Tensei Kon: Katsute no Koutekishu to Konyakushite Saikyou Fuufu ni Narimashita

With their nations in conflict, the Hero Reid and the Sage Elria had long been on opposing sides of the battlefield. However, it would all come to a much too sudden end with the Sage's passing. Single-handedly breaking through the enemy ranks to see Elria one last time, Reid meets his own heroic demise...

But then, he opens his eyes as a newborn a thousand years later, getting another chance at life…and love?!

(Source: Manga UP! Global)