Have you ever seen dōjinshi?
Dōjinshi (同人誌) is the Japanese term for self-published manga, sometimes include novels. Dōjinshi are often the work of amateurs, though some professional artists participate as a way to publish material outside the regular industry. Groups of dōjinshi artists refer to themselves as a sākuru (サークル, circle), and in many cases each sākuru consist of members with the same favorite manga or anime. A number of such groups actually consist of a single artist: they are sometimes called kojin sākuru (個人サークル, personal circles).
I’m crazy for dōjinshi, and I have several hundred dōjinshi on Gintama, Reborn!, Sengoku Basara, Uta no prince sama, and everything else. The piece of them is here.
Dōjinshi is worked by amateurs, but they have professional-level proficiency. They build side stories of some manga or anime, and create our paradise. Sometimes our favorite characters fall in love, and sometimes powerful and heroic battles unfold. Dōjinshi offers a different way of how to enjoy manga that has even attracted otaku, and the market is estimated at more than 50 billion yen.
You can get Dōjinshi at The Comic Market, and Dōjinshi stores like “Mandarake”, “Toranoana” and “Animate”. The average price of them is from ¥500 to ¥2000, depends on the page count.
You can get some dōjinshi on Amazon.com.