[3][4] He said in an interview that in the late 1970s when he wanted to get into directing, he wrote a script for a pink film and brought it to the Ōkura Eiga studio but they told him he needed to start as an assistant director.
[5][6] The Weissers dub Hiroki "the prince of youth porn" for his 1984 film produced by Yū Pro and distributed by Nikkatsu, Teacher, Don't Turn Me On!, once again scripted by Rokurō Mochizuki and featuring Tōru Nakane as the college-age tutor of a high-school girl.
[5][9] Also in 1986, Nikkatsu released Hiroki's creative but bizarrely titled Yū Pro production SM Class: Accidental Urination promoted as "New wave S&M with a sense of humor".
[10] In October 1987, Hiroki directed pioneering AV Idol Hitomi Kobayashi in the pink film The True Self of Hitomi Kobayashi released by Million Film[11] and the next year supervised another early AV actress Eri Kikuchi in Eri Kikuchi: Huge Breasts released by Nikkatsu in January 1988.
[12] Hiroki also ventured into the adult video (AV) world, directing for Athena Eizou, a company founded by former pink film director Tadashi Yoyogi, with titles such as the August 1989 Vanana Baby (ヴァナナベイビー) starring Mako Hyuga[13] and the May 1990 video Nyū sekushī meitsu nukenukefinisshu dai kyōran (ＮＥＷセクシーメイツ ヌケヌケフィニッシュ大狂乱).
[19] Hiroki's breakthrough into mainstream film, however, came with his 1994 feature 800 Two Lap Runners which looked at teenage heterosexual and homosexual relationships against a track and field background.
[20][21] Hiroki returned to his theme of the emotional and sexual lives of young adults in modern urban Japan in his June 1996 film Midori about a high-school girl pretending to be ill in order to see her boyfriend.
[23] Hiroki's 2003 film Vibrator, based on the novel by Mari Akasaka and starring Nao Omori and Shinobu Terajima, returned to his theme of alienated women.