In the fantastical Land of Ooo, the little robot BMO is on a new adventure. Now settled in a new neighborhood with new friends, BMO approaches each challenge he faces with his unique brand of enthusiasm and curiosity in a quest to learn and fill his database.
Wataru, a fourth grader, is once again taken to Shinbukai, a world in another dimension, as its savior, ten days after he had last returned from there. He heads for the Soukaizan, invaded by the Donarukami family from the dark world. Wataru enters the Soukaizan with Himiko and Shibaraku. As they meet new friends along the way, they also bravely confront their enemies. Will Wataru be able to stop the Donarukami’s plot?