My Melody opens a cake shop in Mariland. After encountering a heart in the forest, strange things start happening around her. Meanwhile, Kuromi's Japanese sweets shop across the street is always empty. Kuromi searches for the secret to My Melody's cakes. My Melody and Kuromi work hard to prepare for a sweets-making contest judged by the world-famous pastry chef Pistachio. However, no one knows that this will lead to an incident that threatens the fate of Mariland.