Koukyoushihen Eureka Seven: Pocket ga Niji de Ippai

Renton and Eureka grew up together and formed a bond strong enough to survive even the strange condition that keeps Eureka away from sunlight. Then she is taken from him. Powerless to stop it, Renton swears that one day he will become strong enough to bring her back.

Years later, he serves in the military's Independent Youth Unit 303 and pilots the bio-mechanical Nirvash with exceptional skill. Humanity is fighting a mysterious alien invasion, but Renton does not know that the military's plan to end the war is tied directly to both him and Eureka. His promise to save the girl he loves now stands in the path of a scheme that may demand her sacrifice.