First, focus on the relationship between Shirahoshi and the OC. Decide if it's a friendship, a mentorship, or something more romantic. For example, if it's a friendship, they could have adventures together exploring the underwater world. Second, introduce a conflict. It could be something like an evil pirate group threatening Fish - Man Island or a misunderstanding within the fish - man society about the OC. Third, let the characters grow. Shirahoshi might become more confident with the OC's support, and the OC could learn about the importance of protecting the ocean and its inhabitants.
One common theme is adventure. Since One Piece is all about adventure, many fanfictions with Shirahoshi OCs involve her going on new quests or exploring uncharted areas in the One Piece world.
Sure. You can try searching on fanfiction websites like Archive of Our Own. There are often many great works about Shirahoshi's original character interpretations there.
The OC could be a young inventor who comes to Fish - Man Island to study its unique technology. There, they meet Shirahoshi. The OC creates a device that helps Shirahoshi communicate more easily with the surface - dwellers. In return, Shirahoshi shows the OC the hidden secrets of the Fish - Man Island, and they form a strong friendship that transcends the differences between humans and fish - men.
Many 'One Piece Robin x OC fanfiction' works explore the theme of acceptance. The OC, being an outsider in the One Piece world, has to be accepted by the characters, especially Robin. And Robin, with her own past, also has to accept the presence of this new character in her life. There's also the theme of growth, both in terms of power and character, for both Robin and the OC as they interact and go through various experiences together.
One common theme is adventure. Since One Piece is all about adventure, the OC usually embarks on various adventures in the world of One Piece while building their harem. Another theme is the development of relationships. There's the building of romantic and sometimes platonic relationships between the OC and the harem members.
One idea could be that the OC is a long - lost relative of a Straw Hat member. For example, an OC who is related to Luffy and has a unique power of their own, like the ability to control the weather in a small area. This could lead to interesting storylines where the OC helps the crew during difficult battles or in traversing dangerous seas.
One common theme is adventure. Since it's set in the One Piece world, the OC and Thatch often go on adventures together. Another theme could be love and friendship, as their relationship is explored.
Common themes include exploration. The OC explores not only the physical world of One Piece but also the complex relationships in the harem. Cultural differences can be another theme. The OC might come from a different background and has to adapt to the unique cultures in One Piece. And finally, the theme of loyalty. The OC has to show loyalty to the harem members and vice versa for the relationships to work.
You can start by giving the OC a unique backstory. For example, if they were an orphan like Ace, it could create an instant connection. Also, decide on their personality traits. Are they shy and reserved or bold and adventurous? Their skills are important too, like being a great navigator or a skilled swordsman.