A spaceship carrying powerful, mysterious life forms crashes into a dying planet, releasing an explosion of energy that restores the world with life-generating force. Popo, the protagonist, lives peacefully with his mother in a remote forest inhabited by praying mantises, ladybugs, beetles, and other insects. His primary wish is to become strong enough to find his father, the former Guardian of the Forest, who left years ago to pursue research on the planet and vanished without a trace.
While walking through the woods, Popo encounters a sinister mist that engulfs the forest. The malevolent Passer appears, labeling Popo’s father as an enemy and the cause of the forest’s troubles. Upon returning home, Popo is horrified to discover his mother has been transformed into a half-plant, half-human creature. Believing only his father can restore her and save the forest, Popo sets out on a journey to find him.
The villain Adder and his minions attempt to stop Popo using giant beetles that attack him relentlessly. Fortunately, Popo is aided by Mushiking, the King of Beetles. With immense strength and a dominant fighting style, Mushiking intervenes at critical moments to rescue Popo from defeat and keep him on his path. As Popo embraces his destiny as the next Guardian of the Forest, guided and protected by Mushiking, his epic quest to reunite with his father and save his home begins.