No. 6 is a Japanese anime series based on the novel of the same name by Atsuko Asano. Set in a dystopian future, it follows the story of Shion, a boy living in a seemingly perfect city called No. 6. His life changes when he meets Nezumi, a mysterious boy from the outside world, leading Shion to question the society he lives in. The series explores themes of friendship, freedom, and the consequences of a controlled society. As Shion and Nezumi navigate challenges together, they uncover dark secrets about No. 6 and its true nature, ultimately seeking to change their fates.