No. 6

No. 6 was originally conceived by author Atsuko Asano as a dystopian science fiction light novel series, which was published in Japan between 2003 and 2011. Set in a sterile, controlled city-state following a catastrophic world war, the narrative explores themes of totalitarianism, social stratification, and the complex relationship between the sheltered protagonist Shion and the mysterious fugitive Nezumi. The story emerged during a period of rising interest in YA speculative fiction that challenged the rigid structures of post-industrial society.

The series gained significant cultural visibility following its adaptation into an anime by studio Bones in 2011, which introduced the characters to an international audience. While Asano provided the source material, the aesthetic transition to visual media helped solidify the iconic character designs that define the series today. Critics and readers generally received the work as a poignant exploration of moral ambiguity, specifically noting the depth of the central character bond as it navigates the harsh, dehumanizing environment of the titular city.