In the near future...
All offspring are rounded up and raised on an island called the "Juvenile Circle." Until they're 18, they receive their education there before transitioning into adulthood. After graduating, a boy named "Shizu" experienced unusual pangs of unease. Were they centered on being a grown-up? Did he want to stay a child? It was neither. Shizu was enveloped by anxiety, which propelled him to discover the "truth" about his society.