There's a fanfic called 'Luffy and the Celestial Dragon's Secret Alliance'. In this story, Luffy forms an unexpected alliance with a Celestial Dragon who has different ideals. It's full of action and character development. The writer does a great job of showing how Luffy's values can influence those around him, even a Celestial Dragon. The story also delves into the politics and power dynamics within the One Piece world, making it a really engaging read.
In this fanfic, Luffy might team up with some of the oppressed people against the Celestial Dragons. For example, he could meet a group of slaves who were once owned by the Celestial Dragons. Luffy, being the freedom - loving pirate he is, would vow to free all of them and take on the Celestial Dragons in a big showdown. They could use their wits and Luffy's unique abilities to outsmart the arrogant Celestial Dragons.
The contrast between Luffy's values and the Celestial Dragons' ways. Luffy represents freedom and equality, while the Celestial Dragons are known for their tyranny. This clash creates a lot of potential for exciting storylines.
A possible plot is that a group of Celestial Dragons decide to hunt Luffy for sport. But Luffy turns the tables on them. He leads them on a wild goose chase across different islands. Along the way, he befriends some of the local animals on each island and uses them to play tricks on the Celestial Dragons. For example, on an island full of monkeys, he teaches the monkeys to steal the Celestial Dragons' hats and run away with them, leaving the Celestial Dragons frustrated and looking rather silly.
One Piece was a very popular manga and animation with a large number of fans. If the main character of a One Piece Doujinshi novel was with Luffy, it might attract some One Piece fans, especially those who liked the characters and storyline of the novel.
However, the quality and popularity of doujin novels depended on many factors, including the content, plot, character setting, and writing style of the novel. If the storyline and character settings of the novel were different from the original One Piece and could attract enough readers, it might become a popular doujinshi novel.
Doujinshi was a unique form of creation that could bring different experiences and imaginations to those who liked the original work. Therefore, if the main character of a pirate doujinshi novel was with Luffy and could attract enough readers, it might become a popular work.
It could be a time - traveling version of Blackbeard. Maybe he also discovers time travel and uses it to his advantage to stop Luffy at every turn. He could go back in time and try to prevent Luffy from getting important allies or Devil Fruits.
He might face powerful enemies. Maybe a new pirate crew with a devil - fruit user who can nullify Luffy's powers. Luffy would have to find a way to overcome this power - nullifying ability to reach Ace.
In a plotline, Luffy could find himself in a strange and magical island where Ace is being held. The island has its own rules and obstacles. For example, there could be illusions that try to mislead Luffy. But Luffy, with his unwavering belief in saving his brother, overcomes these illusions. He might also meet some friendly locals who help him understand the secrets of the island and finally reach Ace. Then he'd engage in a fierce battle with the captors to free Ace.
One idea could be Luffy travels back in time to the era when Gol D. Roger was still alive. He could learn from Roger about the true nature of the One Piece and gain new insights to use in his own journey. Another could be that he goes back to a time when the Straw Hat crew was just forming and he gets to relive those early days with new knowledge, making different choices to strengthen the crew faster. Maybe he travels to a future time to see the consequences of his actions and then comes back to change things for the better.