Kakugo no Susume
English title: Apocalypse Zero
Japanese title: 覚悟のススメ
Type: OVA
Source: Manga
Episodes: 2
Status: Finished Airing
Aired: Oct 23, 1996 to Dec 18, 1996
Duration: 37 min per ep
Rating: R+ - Mild Nudity
Studios: Ashi Productions
Producers: Victor Entertainment, Big West
Licensors: Media Blasters
Genres: Action, Horror, Sci-Fi
Themes: Gore, Mecha, Mythology, Super Power
Demographics: Shounen

A series of natural disasters has reduced the world to rubble, with the survivors doing whatever they must to survive in a world gone mad. But one young boy, Kakugo, gifted with amazing martial arts and a superpowerful suit of armor by his late father, has been charged with making the world (or at least his school) a safer place. But his sister has a matching set of skills and equipment, and she`s on a mission to bring peace to the world... by wiping out humanity! 

(Source: AnimeNfo)