Ensign Yuu Kajima, a fighter pilot and the sole survivor of his unit, was chosen to become the leader of the 11th Autonomous Mechanized Composite Corps (nicknamed "Guinea Pig Team"), an experimental unit created to test Mobile Suit equipment. During a mission, Yuu and his team encountered an unknown blue Mobile Suit with overwhelming power that attacked both friend and foe alike. This encounter marked the beginning of Yuu's involvement in a conspiracy surrounding the mysterious EXAM System.