Suzu is a 17-year-old high-school girl living with her father in a rural of Kochi Prefecture town, a textbook definition of depopulation in the Japanese countryside. Wounded by the loss of her mother at a young age, Suzu one day discovers the massive online world "U" and dives into this alternate reality as her avatar, Belle. Before long, all of U's eyes are fixed on Belle, when, one day, a mysterious and infamous dragon-like figure appears before her.