An astronomer spots a black cloud heading toward Earth, threatening to eradicate all life, yet no one believes him since global governments are preoccupied with waging war. Meanwhile, boy detective Kenichi, the young Rock Holmes, Shunsaku Ban (Mustachio), and others uncover the Fumoon, a species of tiny, telekinetic humanoids that evolved in Australia, who have their own strategies for handling the impending apocalypse.