Seventeen-year-old high school student Naito Suzu lives in the rural countryside of Kochi, rich in nature. After losing her mother in an accident when she was young, she lives with her father. Since her mother's death, she has been unable to sing, and writing songs has become her only lifeline. One day, encouraged by her best friend, she joins a virtual world called U, where over 5 billion people gather online. In U, she creates her avatar, known as As, and lives an entirely different life. Although Suzu couldn’t sing, her avatar, named Bell, naturally sings. Bell's songs quickly gain popularity, making her a beloved figure worldwide. On the day of a grand concert gathering millions of As, a mysterious being called Dragon suddenly appears before Bell with a thunderous roar. The concert is thrown into chaos by the violent and arrogant Dragon.