Tensura: The 8th Primordial

When Haru of the Minamoto dies standing after a heroic effort during the Genpai War. He is reincarnated in the world of That Time I Got Reincarnated As A Slime. As a demon??? In the Underworld??? As a bottom feeder???? Watch Haru climb the ranks of the Demon Ladder and maybe someday stand toe to toe with the monstors of the Underworld and the Cardinal World — Description from novelcodex.org