Japan Image Upload Laws

If someone were to post an unauthorised image of a person on a porn site, what are the charges that could be brought against that person?  Last week, Tokyo police arrested a porn site operator who had posted images of female athletes on his website and apparently all that they charged him with, was copyright infringement.  Extracts from a report that provides a possible explanation:

It is difficult to take legal action since there is no law against nonconsensual filming or photo-taking in Japan, and such acts, including taking images of people in nude or sexual situations, are only punishable under nuisance-prevention ordinances set by prefectural governments.