Genetic engineering on trees was conducted at a research facility on the Moon to produce trees capable of growing in harsh, arid conditions. The trees gain consciousness, obliterating Earth's civilizations and destroying the Moon. Three hundred years later, Japan is a dystopia covered by the Forest, a huge expanse of sapient trees, and ruled by the tree-like Dryad, which inhabit the planet and control the water supply of both trees and humans. Agito, a young boy, and his father Agashi, as well as his friends Cain and Minka, live in Neutral City, a city carved out of the ruined skyscrapers which acts as both a buffer and a bridge between the Forest and the militaristic nation of Ragna. While the people of Neutral City co-exist peacefully with the trees of the forest, the nation of Ragna aims to destroy the Forest to restore the Earth.