The Ultra Guard have reports of earthquakes in the area, but there's something strange about them. Meanwhile, two female racers on their way to a rally find an unusual rock just as another tremor shakes the ground near Aosawa Mountains. Moroboshi and the others seek out Dr. Iwamura to help investigate the peculiar quakes in the area. They also find the two girls. The strange rock cluster they found turns out to be Ultonium -- an element found at the Earth's core. The Ultra Guard then board the Magmalizer to burrow below the Earth's surface in the hopes of finding the answers behind the surge of earthquakes.
