APOCALYPSE ZERO

In the post-apocalyptic world that Earth has become in the 21st century, monsters, mutants, and demons all roam the land looking for human prey. Kakugo and Harara have been trained by their father in the ancient Zero fighting technique, to protect the last remnants of humanity, and restore hope and peace on Earth. Powered by both their superior fighting skills and their secret techniques, as well as special living armor made from the souls of ancient warriors, they are sent into the world to defend the weak from demons and mutants who savagely attack and destroy human life. Yet, with all their training, Harara succumbs to the evil within, killing their father and believing Kakugo is dead as well. But their fates are still intertwined. Kakugo comes to the remnants of a city to help the few human inhabitants. As he saves them from the ravages of cannibalistic monsters and depraved mutants, he once again encounters his psychotic sibling, and the bloodiest battle of the 21st century brings new meaning to Sibling Rivalry! (Source: Media Blasters) — Description from AniList community (anilist.co).