Genesis Climber Mospeada (1983)

In the 21st century, Earth is invaded and quickly subdued by a alien race called the Inbit. Years after a failed liberation attempt by the Mars station's forces, a second Terran attack is attempted with a force armed with new weapons vastly superior to the enemy, but again Inbit defenses prove to be too strong. One of the few survivors to reach Earth is Stick Bernard, a young mecha fighter pilot who witnessed the death of his fiancé in the battle. Separated and alone, the aggrieved pilot sets out to attempt to complete his mission to find Reflex Point, the suspected Inbit headquarters, and do what he can to destroy it. Along the way, he meets up others who join to form a small guerrilla unit who must find their way to Reflex Point and stop the Inbit.