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.
おのぼり山への遠足の最中、吼児は広い花畑で山口梢という少女と出会う。吼児は、梢からおのぼり山の自然が土地開発のために失われつつあると聞く。一方、仁たちは、梢の兄の実と喧嘩をしてしまい、邪悪獣デザートスが生まれてしまう！ デザートスは木や草を切り倒し始め…。
