The game takes place inside a storybook. The book's story tells of the dream world of Muu, where the quality of dreams determined the quality of the weather the next day. Because of this, the Muu citizens invented a dream machine so they could always have good dreams. One day, a mischievous being named Mamu invaded the land and used the dream machine to make nightmarish monsters. However, the Muu people learned of his weakness to vegetables and used them to defeat him. The old storybook had found its way into the hands of a pet monkey, Rūsa, who gives the book to the young twins Poki and Piki. However, the twins quarrel and end up ripping out the last page of the book, causing its ending to be erased. Mamu, freed, reaches through the pages and grabs the twins, pulling them into the book. Rūsa gets the twins' parents, Mama and Papa, their brother, Imajin, and Imajin's girlfriend, Lina, and they enter the book to rescue them.