Raiga and Kuuga Kudou are twin brothers who like animals and sometimes help their mother in the zoo where she works. However one day, an alien gang known as Dark Spinner appeared on Earth, aiming to obtain the Earth Energy from the Earth’s rotation and started to wreak havoc on the planet by summoning huge monsters known as Spingers. In the midst of chaos and the attack on their town, Raiga and Kuga heard voices calling to them, leading them to encounter the defense group Earth Granner. Raiga and Kuuga both became pilots of special machines called Gao Granners, and assume a secret identity. These machines can combine with sub-machines in order to become powerful super robots, as humanity’s trump card to protect the planet from the threat of Dark Spinner.