Toriyasu, a fifth-grader, and his little sister, Meeko, are desperate to find their beloved dog Papadoll, who has been missing for a week. They are suddenly visited by two cats who transport them to the faraway land of Banipal Witt, where Papadoll was taken. However, Papadoll has transformed into a monstrous dog due to the planet's harsh sunlight and is now under the control of the wicked Princess Buburina, who has the power to transform people into balloons. With the sunrise looming, Toriyasu, Meeko, and the cats must find a way to rescue Papadoll and the ballooned citizens of Banipal Witt or risk suffering the same fate as their canine companion.