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.