First, you need to understand Zoro's character. He's tough, dedicated to his swordsmanship, and has a strong sense of loyalty. Then, create an interesting backstory for your reader character that can interact well with Zoro's. Also, focus on building their relationship gradually. Don't rush into the romance part right away.
One popular trope is the training together trope. Zoro is always focused on getting stronger, so having the reader character train with him adds an interesting dynamic. Another is the injured Zoro being taken care of by the reader. It shows a softer side to his tough character. And of course, the 'rival to lover' trope where the reader starts as a rival to Zoro in terms of swordsmanship or some other aspect and then they fall in love.
Expect a lot of character exploration. Since Robin has a complex past and Zoro has his own goals and dreams, the fanfiction could delve into how they influence each other. For example, Zoro's pursuit of becoming the world's greatest swordsman might inspire Robin to pursue her own academic or personal goals more vigorously.
In Robin x Zoro fanfiction, their relationship can be really interesting. Robin is the intellectual and mysterious one, while Zoro is the strong and determined swordsman. Their interactions might start from a simple comradeship on the Straw Hat crew. Maybe in some fanfictions, Robin's knowledge could help Zoro in his swordsmanship journey, like providing him with historical information about some special swords or fighting techniques from the past.
Mutual respect is also a big theme. Zoro respects Nami's intelligence and ability to handle money matters for the crew. Nami respects Zoro's strength and his unwavering loyalty. Fanfics often highlight these aspects to show a more complex and interesting relationship between them.
Well, they could be on a mission to find a special treasure. Luffy is all gung - ho about it, and Zoro is just following his captain's lead. Along the way, they face many obstacles, but their friendship keeps them going. For example, Zoro might get injured protecting Luffy, and Luffy, in his own goofy way, tries to cheer Zoro up and make sure he heals quickly.
Friendship is a very common theme. Their unwavering loyalty to each other is often explored. For example, in many fanfics, Zoro will always be there to protect Luffy and vice versa.
A very popular one is 'Beyond Rivalry'. In this fanfiction, it explores the idea of Zoro and Sanji having to rely on each other completely when they are stranded on an uncharted island. It really shows their growth as characters and how their relationship can be more than just the typical rivalry.
One popular storyline could be them getting lost together on a strange island. Sanji's cooking skills keep them fed while Zoro's combat skills protect them from the island's dangers. As they face these challenges, they develop a deeper understanding and respect for each other.
In some fanfictions, their interactions are more emotional. Sanji could be injured, and Zoro would show his concern in his own gruff way. He might stay by Sanji's side to protect him while he recovers. And Sanji, in turn, would thank Zoro in his own unique, sarcastic yet sincere way. Their relationship in these stories is complex and full of nuances.