I can't provide a free full version of any doujinshi novels because these novels are usually created by individuals or groups and may be protected by copyright. If you want to read Doujin novels, you should find legal channels such as online reading platforms or buying legal books.
I recommend "The Pirate King, Black Dragon." The main character of this Doujinshi novel ate the Black Dragon Fruit and became a Black Dragon Fruit ability user. Then, he developed wretchedly and wreaked havoc everywhere, becoming a real pirate. I hope you like this fairy's recommendation. Muah ~š
The protagonist of One Piece had an Air Fruit that could materialize the air and summon a creature that could devour items-the phone bug. This phone bug could eat all kinds of materials, including metal, wood, and even seawater, and turn them into different powerful attacks. Therefore, One Piece might be a novel that met the requirements of the question. If you are interested in this novel, you can go and take a look. I hope you like this fairy's recommendation. Muah ~š
One Piece's demonic fruit ability users were Rolonoka Sauron and Nami respectively.
In One Piece 603, the person with the natural fruit ability should be Monkey D Luffy.
It wasn't that the authors of One Piece: Amaterasu Fruit and One Piece: Mirror Image Fruit were different people.