I understand one thing about doujinshi that sold at comiket, basically it's purely fanmade from original manga or anime. A made off story that mostly for fanservice, pairing characters from different anime and manga. I only read some of it, the books is so thin but the story is interesting. I also found a fact that some doujinshi author is also a mangaka author in real life, take a sample from 'Kakuji Fujita' known for 'Tokugawa no Saru'. The author also made doujinshi with other name as 'Gachi Drunkers', most of the stories theme are pro wrestling. You can google it, but use vpn if it's blocked in your country.

Truthfully I was inspired and someday plans to make a fanmade story, I made a novel with original story and original characters. If I made it crossover with magical girl characters, it would be hilarious.

I was wondering if there is doujinshi that made purely based on original character and story
Can someone give an example of doujinshi that are made with original story and character?
Is there any other mangaka that made doujinshi? Give me any name that you know

Wouldn't doujinshi that made purely based on original character just be a self published one-shot/series?

I'm not sure what you mean, I thought they were just self published mangas (though there is an abundance of fanservice doujinshi ). Do you have a genre in mind?

Some series have one of their characters do a "Doujinshi" about the rest of characters is that what you mean?
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