GEAR Fighter Dendoh (2000)

The Earth Defense Force GEAR was founded to protect Earth from invasion by the Mechanical Empire Garufa. Mankind builds GEAR Fighter Dendoh, the only hope for the universe, to oppose Garufa. While GEAR had chosen pilots themselves, grade schoolers Hokuto Kusanagi and Ginga Izumo end up being chosen by Dendoh itself as it's pilots. They don’t know what to do, but manage to operate Dendoh in the fight against Garufa.