Ginga Kikoutai: Majestic Prince takes place in the latter half of 21st century when humans leave the Earth and begin to live in space. In order to adapt to the environment in space and deal with the hostile aliens in Jupiter, scientists have created genetically engineered children called "Princes." These children are artificially raised, and they are all trained to be pilots of armed robots called "AHSMB" (Advanced High Standard Multipurpose Battle Device).