Set in the near future, as the Earth reaches its end due to environmental pollution, the planet wakes up its ancient sleeping guardian. This guardian just happens to be a flower-like biological weapon that attacks mankind in an attempt to destroy civilization. An all-out battle begins between the surviving humans and the Earth itself. Just as poor rookie pilot, Kay, gets their first assignments, they encounter a different type of guardian. Can this discovery help them defeat Earth’s guardian? Or will they just destroy both themselves and their home world altogether?

A plague-like wind blows across the arid, sandy expanse of a post-apocalyptic Japan. As it sweeps over the living and nonliving alike, rust is all that remains. The cause of this catastrophic state? Mushroom spores. At least, that's what everyone thinks. Enter Akaboshi Bisco. He's known as the "Man-Eating Mushroom," and is a wanted archer whose deadly aim instantly sprouts mushrooms wherever they land. However, in truth, he's a "Mushroom Keeper," committed to spreading fungi to enrich the land and return it to its former state.

Anezaki Satoru had a precious childhood friend, Ichinose Yuna, who was killed by a gang of rapists. Blinded by rage and thirst for revenge, Satoru gruesomely murdered 15 rapists and cut off their genitals, for which he was sentenced to capital punishment. After his death, Satoru regains consciousness in another world where all men have become mindless beasts. Finding himself lost in this world, he meets some of the struggling survivors fighting the hordes of beasts. What he learns is shocking... Yuna is apparently still alive in this world! Satoru chooses to join the fight in order to find his precious friend.