The future city of 2013, No. 6. Shion, who was raised as the highest-ranked elite since he was two years old in the city that realized the ideal of humanity, has been rapidly turning its destiny since he met a boy who calls himself "Mouse" on the night of his 12th birthday. Why did I open the window that night?　I didn't know how to starve, to cry, or to fight. Can I find hope and hope to live in the story of NO.6?”