0verflow (オーバーフロー) (stylized 0verflow) is a Japanese video game division of Stack Ltd. (有限会社スタック) specializing in the production of mature interactive fiction. The Overflow label is known for its game franchise School Days. Stack's headquarters are located in the Sugishō Building (杉商ビル) in Kanda, Chiyoda, Tokyo. Overflow's PureMail video game was adapted into a two-episode OAV in 2001. Overflow's Imouto de Ikou! video game was adapted into a two-episode OVA in 2003.