"[2] When Nikkatsu started their Roman Porno series of mainstream theatrical softcore pornographic films in November 1971, Sone was quickly given his chance to direct.
[1] Later in 1972, Sone switched to contemporary themes with Lusty Sisters,[4] but would return to the period-piece with his popular action-sex film starring Nikkatsu queen Junko Miyashita, Female Ninja Magic: 100 Trampled Flowers (1974).
[5] By the late 1970s, Sone had become associated with a more violent style of eroticism in such films as My Sex Report: Climax Point (1976) and Shinjuku Mixed-Up Street: Wait Till I Come (1977).
"[9] Throughout his career Sone directed many films of lesser quality, such as Overly Ripe Breasts (1973), Modern Prostitution: Lust Under A Uniform (1974) and 100 High School Girls: Secret Motel Report (1975).
Nikkatsu gave Sone the chance to direct the non-Roman Porno series of light comedies, Glory Cheerleaders (1976–1977), which became popular hits.
[11] While continuing to direct for Nikkatsu at this time, Sone worked for independent studios where he could enjoy more creative freedom, and not be tied to the pink film format.