Origin: Spirits of the Past, originally released in Japan as Gin-iro no Kami no Agito (銀色の髪のアギト lit. Agito the Silver-Haired), is an anime movie produced by Studio GONZO in Japan. It premiered in Japan on January 7, 2006, and premiered in the United States on September 24, 2006 at the Fantastic Fest horror film festival in Austin, TX.

Gin-iro no Kami no Agito is the story of Agito, a young boy living in post-apocalyptic Japan set 300 years in the future. This apocalypse was brought about by extensive genetic engineering on trees, conducted at a research facility on Earth's moon, in order to produce trees capable of growing in harsh, arid conditions! The trees became conscious and spread to Earth in a fiery holocaust, wiping out most of modern civilization and fragmenting the moon. Agito's world is covered mostly by the Forest, a huge expanse of living trees, ruled by the tree-like Druids, which now inhabit the earth and control the water supply of both trees and humans. Agito and his father Agashi, as well as his friends Cain and Minka, live in Neutral City, a city carved out of the ruined skyscrapers of an old metropolis. Neutral City acts as both a buffer and a bridge between the Forest and the 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 in order to return the world to the way it was before the mutant trees invaded.

The movie starts with Agito and Cain racing each other to see who can get to the water hole at the bottom of the city first. By disturbing the sanctity of the water hole and angering the Druids, the two boys are separated, and Agito stumbles upon a large machine with cryogenic pods containing dead bodies. Inside the only active pod he finds Toola, a young girl who has been asleep for the past 300 years. He frees her, bringing her back to Neutral City. The Forest is angered by Toola's awakening, since she carries a Raban — a portable personal electronic device, worn as a necklace, that can be used for communication and a variety of other tasks. The Forest fears that she will fall into the hands of Shunack, a soldier of Ragna who was also awakened from sleep, and that he will use her Raban to locate Estoc, a powerful weapon with the ability to wipe out the Forest and restore human control over the world.

Shunack eventually finds out about Toola and marches into Neutral City with his army to persuade her to join him. The Forest sends a giant creature to stop the meeting which Shunack single-handedly destroys, revealing that he has been "enhanced" — he allowed himself to be genetically altered by the Forest in order to become stronger by using the power of the trees. Convinced that finding Estoc is the only way to restore the Earth back to the world which she once knew, Toola joins Shunack in his quest despite Agito's plea not to go. Agito consults his father Agashi, the founder of Neutral City who, as a result of being enhanced, has turned almost completely into a tree. Agashi, with few days left before becoming a tree completely, encourages Agito to save the Forest from Shunack's plan, since destroying the trees would mean the destruction of mankind as well. Agito journeys to the Forest and allows himself to be enhanced, his hair turning gray as a result.

Agito follows Shunack and Toola to Estoc, which turns out to be a huge volcano converted into a mechanized weapon. Estoc, as it turns out, was created by Toola's father, the doctor who had begun the genetic research on the trees, as a safeguard against the new species. Shunack betrays the Ragna army and commandeers Estoc, revealing his true intentions to use the weapon to clear his guilt: it so happens that Shunack worked on the original genetic alteration experiments on the trees, but, becoming impatient, had tried to speed up the alteration process, leading to the catastrophic invastion of the mutant trees. Having a change of heart, Toola tries to stop Shunack from activating Estoc. Agito finds them and has a showdown with Shunack. To save Toola, he lets his enhancement take over him, and he transforms into a tree, essentially killing himself but trapping Shunack in the process. Toola deactivates Estoc and the weapon begins to self-destruct; however, Toola refuses to leave without Agito. The Forest, seeing that Agito can unite humanity and the trees, grants him his life back, allowing he and Toola to escape before Estoc erupts into flames. Having saved both the humans and the Forest, Agito brings peace between all humans and the trees. Toola finally lets go of her past, symbolically throwing her Raban off of a ledge down into the depths of the Forest and learning to live in harmony with the trees at last.

- From Wikipedia