In the southern country of Banana island, the energetic princess and his humble servant Banna invite Anpanman and his friends to their biggest festival "Banana Matsuri". But when they arrive a stormy and cold day bestows the island and withers all the Banana crop. While searching for the cause on the Banana Mountain a water monster appears that threatens to take back the island to the water world. With the help of Banna, can Anpanman and his friends rescue the island from this crisis?