Great Teacher Onizuka (Japanese: グレート・ティーチャー・オニヅカ, Hepburn: Gurēto Tīchā Onizuka), officially abbreviated as GTO, is a Japanese manga series written and illustrated by Tooru Fujisawa. It was originally serialized in Kodansha‘s Weekly Shōnen Magazine from January 1997 to February 2002, with its chapters compiled into twenty-five tankōbon volumes. The story focuses on 22-year-old ex-bōsōzoku member Eikichi Onizuka, who becomes a teacher at a private middle school, Holy Forest Academy, in Tokyo, Japan. It is a continuation of Fujisawa’s earlier manga series Shonan Junai Gumi and Bad Company, both of which focus on the life of Onizuka before becoming a teacher.
Due to the popularity of the manga, several adaptations of GTO were created, including a twelve-episode Japanese television drama running from July to September 1998; a live-action film directed by Masayuki Suzuki and released in December 1999; and a 43-episode anime television series produced by Pierrot, which aired in Japan on Fuji TV from June 1999 to September 2000. A second live-action series aired in Japan during 2012, and two more in 2014. A sequel manga series, titled GTO: 14 Days in Shonan, ran in Weekly Shōnen Magazine from June 2009 to September 2011. Another sequel titled, titled GTO: Paradise Lost, began in Weekly Young Magazine in April 2014.