Katsuhito Ishii started out directing commercials in 1992, picking up a bunch of awards along the way. His first short film, The Promise of August (1996), made waves at the Yubari International Film Festival with a Grand Prix win, which led to his feature debut: Shark Skin Man and Peach Hip Girl. Based on a visual novel by manga artist Minetaro Mochizuki, the film starred Tadanobu Asano—who'd become a regular collaborator—and became Japan's second biggest box office hit in 1999.

Ishii kept the momentum going with Party 7 (2000), another commercial success featuring Masatoshi Nagase, Yoshio Harada, and Asano again. Around 2001-2002, he explored shorter formats with a mix of projects: the 3D animated piece Hal & Bons, the 2D space opera Trava Fist Planet, and a live-action short called Black Room starring Takuya Kimura. He also worked on music-focused content like Music Power Go Go! During this period, he collaborated with Production I.G to create the animation sequences for Quentin Tarantino's Kill Bill Vol. 1.

By 2004, his fourth feature The Taste of Tea earned Best Feature Film at the Hawaii International Film Festival. Two years later, he co-directed Funky Forest with school friends Shunichiro Miki and ANIKI. That same year, Ishii founded his own production company, Nice Rainbow, in October 2006.