Deunan Knute is a young female soldier and the last survivor of the Global War. During a battle, she is rescued by Hitomi, a Second Generation Bioroid. Deunan attempts to escape from a hospital and takes Hitomi hostage, but is stopped by Briareos Hecatonchires, her former lover, who is now a cyborg. She learns that the war had ended months earlier and is now in a Utopian city called Olympus. Its population is half-human and half-clone, a genetically-engineered species called Bioroids. Olympus is governed by three factions: Prime Minister Athena Areios; General Edward Uranus III, head of the Olympus Army; and a Council of Elders. Everything in the city is observed by an artificial intelligence named Gaia from a building called Tartarus. While there, Deunan joins the ESWAT organization to serve as the city’s guardian and befriends Hitomi.
The Bioroids were created from the DNA of Deunan’s father, Carl, making the Second Generation Bioroids her brothers and sisters. However, they have a lifespan much shorter than those of humans due to the suppression of their reproductive capabilities. When the facilities that were used in the Bioroids’ life extension processes are destroyed by a secret faction of the Olympus Regular Army in a terrorist attack as part of its demonstration of fear of the Bioroids, a crisis which requires immediate resolution is formed. The Appleseed data, however, still exists. As the building is destroyed, Hitomi falls asleep.
Olympus is plagued by conflicting factions. At the center of this battle is Appleseed. Along with a top secret strike force, Deunan and Briareos head for the building where the Bioroids were originally created. She activates a holographic recording from her hard drive, in which the location of Appleseed is revealed. Dr. Gilliam Knute, who created the Bioroids, entrusted the Appleseed to Deunan, but was inadvertently shot down by a military soldier. Colonel Hades, the anti-Bioroid activist who destroyed the Bioroid care facilities, reveals to Deunan that Briareos had intentionally allowed his Landmate, large exoskeleton-like battlesuits, to escape. They run to the rooftop with their team killed and get cornered by the Regular Army. Uranus tries to convince Deunan that Bioroids seek to control humans, intent on destroying the D-Tank on Tartarus. Briareos tries to plea to Uranus that the Elders were the ones who planned this; the D-tank, which controls a virus that was originally meant to keep Bioroids in line, was reworked to sterilize humanity. Hades convinces Uranus that trying to negotiate is pointless, and blames Carl for all that has happened before Deunan guns him down. They manage to escape, but they are washed up on a beach, where Briareos confesses all that he had done was to see her again and unconscious. Mechanic Yoshitsune Miyamoto flies over in his landmate and begins repairing Briareos. Deunan takes his Landmate back to Olympus.
Deunan finds that the Council of Elders are able to save the Bioroids and admit they killed Gilliam. They reveal their intentions of using the D-tank virus to sterilize all humans throughout the world, leaving the Bioroids the new rulers of Earth. They required the Appleseed in order to keep the Bioroids alive, but Gilliam found out and hid the data so their plan could never come to fruition. Athena tells Deunan that the Elders had been acting on their own and shut down Gaia once it realized humanity has lessened its hatred towards Bioroids. The Elders state that they will soon die because Gaia regulates their life support systems, but that they are prepared to sacrifice themselves. They activated the city’s fortresses and they are marching towards their location. Athena states that while D-tank’s security system is nearly impenetrable, a shot from the one of the fortresses’ main cannons might puncture the tank and release the virus. Hitomi reveals that her name can shut down the fortresses on the seventh tower. ESWAT begins mobilizing their forces to try to slow down the towers, but suffer heavy casualties due to their weaponry.
Briareos arrives in a Landmate and calls for Deunan to join the battle. Despite the objection of the Elders, Deunan joins Briareos as they reach the tower. Deunan attempts to inputs the password, but a malfunction prevents her from completing it. Briareos allows Deunan to finish the password. The final letter appears by itself, and Deunan secures the D-Tank. Deunan, Briareos, Hitomi and Yoshitsune reunite as the sun rises over the city. The film ends with Deunan stating that over time the sins of humanity will probably get worse, but that there is always the chance that future generations will learn from these mistakes, and she vows to keep fighting for the children, who are “the true new race of man.”