Apocalypse Zero, known in Japan as Encouragement of Resolve (覚悟のススメ, Kakugo no Susume), is a manga series written and illustrated by Takayuki Yamaguchi.

Kakugo and Harara are brothers trained by their father, Oboro, to slay monsters that have begun roaming the streets of a post-apocalyptic, 21st century Tokyo following a devastatingly, powerful earthquake.

To aid them in their quest, Oboro entrusts his two sons with Fortified Armor Shells (強化外骨格, Kyōkagaikokkaku), cyborg exoskeletons forged using the souls of deceased warriors by their grandfather, a former scientist of the Imperial Japanese Army during World War II, Shiro Hagakure.

However, Harara becomes possessed by a mysterious evil from deep within his armor, mutating his body as well as filling him with a desire to destroy all of mankind to help cleanse the Earth of contamination.

Some years later, Kakugo moves to "Reverse Cross High School", located in one of the ruined districts of Tokyo near the castle from which Harara commands their demon army.

The US license for Apocalypse Zero was acquired by Media Blasters who created a dubbed English language version of the anime translated by Takashi Sakudo and produced by Bang Zoom!

Due to the use of gratuitous violence and repulsive imagery, critical reception to Apocalypse Zero in the west has been largely negative.