Onani Master Kurosawa

One of the best obscure manga out there is a doujin (amateur) work called "Onani Master Kurosawa"... or translated more completely, "Masturbation Master Kurosawa." Despite the name, it's not a pornographic story. It's a very good manga about growing up. The art itself is a very sketchy style, which I personally really like. While this manga is not porn, it does deal with mature issues and is probably best for late high school age and up.

If you want to read it, here's a file with all chapters of the manga as well the special short story that takes place after the last chapter. I highly recommend it. Enjoy!