Takuma Kugayama is a young AS pilot working for the terrorist group known as A-21. In episode 9 , Takuma is taken into top secret custody by the Japanese government after nearly strangling an airport officer to death in Narita International Airport. Takuma's sudden outbursts of violence are a side effect of the drug, "TI-971", he was given to help him control the Lambda Driver that is so vital in piloting the Behemoth.
Although not at all related by blood, Takuma believes that Seina is his older sister. In reality, Takuma had killed his own older sister some time before the beginning of the series. His only real goal is to please Seina and make her proud. Seina, however, is only using Takuma's ability to pilot the Behemoth so that she can exact her revenge on the world.