Eldran piloting the mecha Raijin-Oh crash lands into Hinobori's elementary school. With the last of his powers, Eldran saves the ones in the school at the moment: class 3 of the 5th grade. He entrust them with Raijin-Oh and the duties to protect the Earth, while Eldran goes into hibernation to recover his powers.

Class 5-3 gets a visit from the army, demanding to hand over Raijin-Oh. The arguing is interruped when Jaku Beast Dustoron is running loose in the city. After finding out that only Class 5-3 can operate Raijin-Oh, the army has no choice but leave Class 5-3 alone.

The entire Class 5-3 average match score of the last test is far below the rest of the other classes and needs to do a retest. Asuka, Kouji, Maria and Tsutomu are assigned to help Jin with his studies as his test score is zero. Jin tries to run away, but in the end can't escape. The next day, right before the retest, Jaku Beast Testora appears and Class 5-3 needs to sortie. After defeating the Jaku Beast, Class 5-3 does the retest much to the dismay of Jin. A couple of days later the tests are graded and Jin has 80 points.

During an excursion, the boys of class 5-3 gets into a fight with the boys from the local. Meanwhile Kouji meets a girl called Kozue, who explains that the locals are angry that more and more trees are being cut for the expansion of the park for tourists. The next day, Class 5-3 hears that Onoboori mountain (the place they went yesterday) became treeless and a Jaku Beast is attacking. Still remembering the fight, Jin is reluctant to sortie. Kouji insist, saying it's their duty as the defenders of Earth and manage to convince everyone including Jin. With the help of the locals Raijin-Oh manage to defeat the Jaku Beast.