Pink(1999)

Pink is the story of a young high school student named Usaki who is trying to become an adult porno artist. Who would've figured that out of a such a cute, innocent blond boy? Guiding him is Benio, the original artist of the story that Usaki is working on. Benio at first seems to just want to teach, but then finds himself getting a little too interested in teaching Usaki how to get into that, er, certain frame of mind for drawing adult porn.

Now enter in Usaki's father, an attractive, sexy man who is more than a little interested in Benio, and makes no move to hide it both from Benio and his own son. And who could resist that? Who would want to?