The anime Simoun is online to watch with full episodes of the Japanese anime series.  Simoun is an anime which takes place on the planet Daikuriku.

This is an earthlike planet that is populated that look like humans. However in this planet everyone is female until the age of 17 when they chose their premanent sex. At one point Daikuriku was more technologically advanced culture flourished, but it has since crumbled, and much of its technology has been lost.

Watch Simoun Online
Catch full episodes via this link