One way could be by focusing on their different personalities. Luffy's carefree and determined nature, Vivi's strong sense of loyalty and leadership. In the harem aspect, other female characters might be added. For example, Nami could be part of it due to her long - time relationship with Luffy. They could all go on adventures together, with Vivi guiding them in some aspects as she has knowledge of the Arabasta kingdom. The story could also explore how they all deal with the power of the One Piece world, with Luffy's goal of finding the One Piece at the center.
Well, in such a fanfiction, the story might start with Vivi joining Luffy's crew more permanently. Since Luffy is always open - minded and accepting, a harem could form around him. The female characters in the harem would respect Vivi as a princess. They could work together to protect the Straw Hat crew. For instance, during battles, Vivi could use her knowledge of politics and strategy, while the other female characters use their combat skills. This would create an interesting dynamic within the harem and the crew as a whole.
Luffy would be the central figure. His relationship with Vivi is one of friendship and mutual respect. In the context of a harem, Luffy might not fully understand the concept at first. Vivi, on the other hand, could act as a mediator or an equal partner among the female characters in the harem. The harem members could all be united by their admiration for Luffy and his noble goals.
The relationship could start with mutual curiosity. Luffy might be curious about Monet's unique abilities as a half - snow woman, like her ability to create snow and ice. Monet, on the other hand, could be curious about Luffy's unwavering will and his strange rubber powers. This initial curiosity could lead to them spending more time together and gradually building a bond.
The OC can be developed by having them learn from Vivi's strong sense of loyalty and duty to her kingdom. For example, if the OC was a bit of a carefree spirit before, seeing Vivi's dedication could make them more responsible. They could also develop their fighting skills by training with Vivi, who is no stranger to combat situations in the One Piece world.
The popularity comes from the unique relationship between Luffy and Vivi in the original 'One Piece' series. Their friendship is very special, and fanfics allow fans to explore it further.
Their relationship can be developed through shared adventures. For example, when facing a really tough enemy, Luffy's determination to protect Robin and Robin's trust in Luffy's strength can bring them closer. Each time Luffy saves Robin from danger, it deepens her respect and loyalty to him.
Well, perhaps the plot could start with Vivi leaving her kingdom again to join Luffy on his journey for some important reason. As they travel, they face numerous difficulties together and rely on each other more and more. Their friendship gradually turns into love. When Vivi becomes pregnant, it causes a stir among the crew. Some are overjoyed, while others worry about the implications. Luffy, being the captain, has to make decisions about how to keep Vivi safe and still pursue their goals. And there could be a sub - plot where other characters from the One Piece world react to this news, either with envy or with plans to use the situation to their advantage.
They could have heart - to - heart conversations. For example, Shanks could share his past adventures and the lessons he learned from them with Luffy. This would help Luffy gain more wisdom and also deepen their connection.
In some harem fanfictions, Luffy may develop more emotional intelligence. For example, he has to understand the feelings of the different girls in his harem. He might become more perceptive about relationships compared to his rather straightforward self in the original series.
There's also 'Luffy and Vivi: Reunion'. This fanfic focuses on what happens when Vivi reunites with the Straw Hat crew after a long time. It beautifully captures the emotions and the unbreakable friendship between Luffy and Vivi, with some really exciting action scenes in between.
One popular type of 'One Piece' fanfiction involving Luffy and Dragon might be about their eventual reunion. Since Dragon is Luffy's father, many fans like to imagine the moment when they meet again. In some fanfictions, Dragon could be secretly guiding Luffy's journey without him knowing. This adds an interesting layer of mystery to Luffy's adventures as he is unknowingly following a path his father has some influence over.