A long time ago, the humankind fought a fierce war against the evil Kingdom of Jamatai. On one side, Queen Himika, a mysterious sorceress who commands a legion of giant warriors called Haniwas; on the other side, the crew of the Buildbase, guided by professor Senjiro Shiba, and Steel Armor Jeeg, the invincible giant! At the end of the final battle Jeeg finally won, and Himika was imprisoned under the soil; but an unexplicable phenomenon created by the clash between two different energies, generated a dark cloud which swallowed the whole island of Kyushu...

Fifty years have passed from that day, when at Shimonoseki, the nearest Japanese city to Kyushu, a new Haniwa appears to destroy the town and bring back dark memories of the past. But the new Buildbase crew is ready to fight!
Fly, Big Shooter, and launch the parts that will create the new Steel Armor Jeeg! Come back to life, Jeeg, and fight against the Kingdom of Jamatai to reconquer the land lost to Himika half a century ago! It's time to fire your Knuckle Bomber!