Satou is a ZAFT soldier loyal to the former PLANT chairman Patrick Zala to eliminate all Naturals, after the lost of his girlfriend and daughter in the Bloody Valentine Incident. Blind with rage and hatred, he refuses to accept PLANT's truce after the end of the First EA-PLANT War and decided to destroy all Naturals by dropping a wreckage of Junius Seven to Earth to avenge his family and the previous chairmen.

(Source: Gundam Wiki)