Well, in this fanfiction, perhaps the relationship between Luffy and Rayleigh is explored in more depth. We might see Rayleigh sharing his old tales of the Pirate King Gol D. Roger with Luffy. This could inspire Luffy even more in his journey to become the Pirate King. Also, Luffy's character growth in terms of leadership could be a great part. Under Rayleigh's guidance, he might learn how to better lead his crew and make more strategic decisions during battles.
In the 'Luffy trained by Rayleigh fanfiction', it could be fascinating to see how Luffy's willpower is strengthened. Rayleigh might put Luffy through some really tough training regimes that test not only his physical strength but also his mental resolve. And the way Luffy adapts to new fighting styles taught by Rayleigh would also be interesting. Maybe he combines his own unorthodox fighting with Rayleigh's more refined techniques to create a whole new and powerful combat style.
Probably, the main plot is about Luffy's transformation under Rayleigh's training. Rayleigh could be teaching Luffy about the secrets of the Grand Line, the lost history, and advanced combat skills. Luffy then uses what he has learned to face new and more powerful enemies. For instance, he might encounter some strong pirates who are also after the One Piece, and he has to use his newly acquired skills to defeat them and protect his crew. The plot could also involve Luffy's crewmates waiting for him during his training and their own mini - adventures in the meantime.
Another aspect could be that the OC has a strong sense of justice. Rayleigh is associated with the Roger Pirates who had their own sense of adventure and justice. The OC could inherit this value and strive to make the world of the fanfiction a better place, perhaps by fighting against the corrupt elements in the pirate world.
The character interactions. Luffy's carefree and fearless nature can lead to some hilarious and heartwarming interactions with the characters in DxD. For instance, his interactions with the devil kings or the angels can be full of surprises. He might befriend some of them in ways that are unexpected, based on his simple view of good and bad.
The OC would stand out in terms of physical abilities. With Rayleigh's training, it could have enhanced strength, speed, and endurance. For instance, it could run faster than most characters or lift heavier objects with ease.
The relationship between Harry and Dumbledore in this fanfiction can be really fascinating. Dumbledore is a very powerful and wise wizard, and his training of Harry might involve not only magic but also life lessons. They could have some deep conversations that shape Harry's view of the wizarding world and his role in it.
Well, the plot could involve Luffy being taken under Whitebeard's wing after an encounter. Whitebeard, seeing Luffy's potential, decides to train him. Luffy would then be exposed to the different fighting styles of the Whitebeard pirates. He'd probably have sparring matches with the stronger members, like Marco. This would make Luffy even stronger and more well - rounded in his abilities.
Perhaps Dragon would also introduce Luffy to some new allies or inform him about the greater political and power struggles in the world of One Piece. This would give Luffy a broader perspective and help him understand the significance of his actions. He might learn about the true nature of the World Government and how to better fight against it, not just for the sake of his crew and friends, but for the freedom of the entire world.
One possible plot could be that Luffy, realizing he needs to become stronger in a different way, seeks out Mihawk. Mihawk, seeing potential in Luffy, decides to train him. Luffy would have to endure intense swordsmanship training, which is quite different from his usual combat style. This would also lead to some interesting character development as he struggles to adapt to Mihawk's strict training regime.
The power comparisons are really interesting. Luffy's ability to stretch and his Gear forms against Naruto's Rasengan and other jutsu. It's like a clash of two very different power systems.
One interesting aspect could be the exploration of Sabo's emotions. He has a deep connection to both Ace and Luffy. In the fanfiction, it might show how he misses Ace and his unwavering loyalty to Luffy. For example, it could describe his memories of their adventures together as kids, which would be really nostalgic.