大九明子

Ōku was born in Yokohama, Kanagawa. In high school, she joined a rakugo group. While studying Politics and Economics at Meiji University, she was part of a student theatre troupe. After graduating, Ōku briefly had an office job at a subsidiary of the Ministry of Labour. She then entered a comedy acting school for one year and performed as stand-up comedian, and afterwards, at age 27, she entered Eigabi School, a film school where director Kiyoshi Kurosawa taught, among others.

While still at film school, Ōku won a screenwriting contest with a script that would become her theatrical feature film debut as director, 意外と死なない (Igaito shinanai, literally "don't die unexpectedly").