Recently, Kampachi Hazama dreams that he is wearing a ribbon on his chest. Even without it, strangers often confuse him as a girl, and his classmates call him “princess” because of his feminine appearance. His childhood friend Shintaro doesn't mind, telling him that he's worrying too much about it. Nevertheless, Kampachi still wishes to “become a burly boy some day."

One day, he is drawn in by a mysterious book he finds in the library and meets Marianne, who calls herself "the strongest witch in history." She asks Kampachi, who has a witch's magical talent despite being male, "Would you like to become my apprentice?" Before Marianne can finish her words, the ribbon Kampachi saw in his dream sprang out from his chest and wraps all around him. When the ribbon is undone, Kampachi has been transformed into a female body...!