Kodaigon was originally a statue that resided in the middle of a shrine in a small village and was hailed as both their god and guardian. When Alien Grotes came to Earth in hopes of killing Captain Ryu Ibuki of MAT, Grotes stole the Kodaigon statue and injected it with a special serum of his race that brought the statue to life as Grote's juggernaut enforcer.

Alien Grotes first unleashed Kodaigon onto the village during a worshipping ceremony, but was called back by Alien Grotes once Grotes was discovered by the captain. The next day, Alien Grotes summoned Kodaigon yet again, this time to attack the village directly, Grotes marching behind Kodaigon, using the statue as a walking shield to protect him.