 After buying a worker mech for his business with his girlfriend Elina, they discover it is actually a "Metal Slader", a military grade mech used during the war.The machine holds a secret message saying Earth is in danger and to seek the "creator".Tadashi, Elina and his younger sister Azusa decide to fly to the nearby space stations and colonies near Earth and the Moon to investigate the mech's origins and the meaning of the strange message.