Self(2008)

Self

Youichi is a very serious, stoic young man with a girlfriend and a regular sex life. However, he has never experienced sexual self-gratification.

Recently, he's become aware of a book called "Masturbation" at the library he works at -- an educated discourse into the history of the sin of Onan and related practices. Finding himself increasingly intrigued by the concepts within, he begins to conduct a series of experiments ... Join him as he embarks into a whole new world!