Ontama are colorful musical spirits that exist in the world of Ontamarama, a peaceful world of beauty and natural rhythm. Ontama are extremely precious to the people there because their playful nature and soothing music bring happiness to everyone; Ontamaestros devote their lives to study the Ontama and learn how to orchestrate them to make music.

A young boy and girl, Beat and Rest live on a small tropical island in this world. As childhood friends as well as friendly rivals who aspire to become famous Ontamaestros, they compete to see who will be the one to achieve their dream first. One day, on their way back home from the OntaConservatory, where they study to become Ontamaestros, Beat and Rest find a weakened Otama in the middle of the road. This surprises them because Otama rarely appear in these places. It turns out that Blast, a demon seeking power, is capturing all of the Otamas. The player picks to play as either Beat or Rest, and must play against various enemy ontamaestros who use captured Otamas.