Hachigatsu no Cinderella Nine (Japanese: 八月のシンデレラナイン, Hepburn: Hachigatsu no Shinderera Nain, "Cinderella Nine in August") is a free-to-play mobile video game for iOS and Android published by Akatsuki and Kadokawa. It was released in Japan on June 27, 2017. A four-panel comedy spin-off manga series by Bkub Okawa titled Hachi Nai Gaiden: Senryoku Gai! Katato-chan (ハチナイ外伝 戦力外！カタトちゃん) and a novelization titled Hachigatsu no Cinderella Nine ～Before Summer～ (八月のシンデレラナイン ～before summer～) are being serialized on the game's official website. A 4-episode original net animation adaptation of the four-panel manga titled Katato the Animation (カタトTHEアニメーション) was streamed between May and June 2017, and an anime television series adaptation of the original game by TMS Entertainment aired from April 7 to July 7, 2019.