“Roman Porno” (from the words 'romantic pornography') is a genre of Japanese theatrical softcore erotic films produced/distributed by Nikkatsu from November 1971 to May 1988. A total of over 1100 films were produced during the 17 years, with several hundreds of them produced by other companies for and distributed by Nikkatsu.
This site is all about this special genre of 'pink film' (surprise!). So go forward and check out the complete list of roman porno movies (it is looong) or available DVD releases. The individual movie pages (linked to in the list) will also link to available VOD releases but unfortunately those are only for Japanese residents.