Some good ones include 'Rook's Protective Side'. In this fanfiction, the reader is in danger and Rook shows his very protective side towards the reader. It's a great read if you like to see the relationship develop from a more protective angle. Additionally, 'A Day with Rook' is a lighter fanfiction that just shows a normal day in the life of Rook and the reader, with some cute interactions and dialogues.
One possible plot could be that Rook and Ben go on an adventure to a new planet in the Ben 10 Omniverse. They encounter a strange alien species that has a unique power. Ben tries to use his Omnitrix to transform into an appropriate alien to deal with the situation, but there are some glitches. Rook, with his Plumber skills, helps Ben figure out what's wrong and together they overcome the challenges and make new friends among the aliens.
Another way is by showing their daily interactions. Like when they're just hanging out between missions, sharing stories about their different worlds. Ben could tell Rook about his adventures on Earth, and Rook could share stories about his Plumber training. This would make them understand each other better and grow closer. They could also have inside jokes that develop over time from these interactions. Also, having them train together to improve their combat skills would not only make them better fighters but also strengthen their relationship as they rely on each other during the training sessions.
First, think about the character of Rook. What are his traits? His loyalty, his sense of duty. Then, create a scenario for the reader to enter his world. Maybe it's through a time - space anomaly. Keep the interactions between Rook and the reader natural. For example, Rook might be initially cautious around the reader as he is with new things.
Perhaps a story where an old enemy of Ben's targets Rook to get to Ben. Ben feels guilty and protective. They go on the run, hiding in different places across the galaxy. Along the way, they meet some interesting characters who help them. In the end, they face the enemy together, with Ben using his Omnitrix and Rook using his upgraded Proto - Tool to defeat the bad guy.
An interesting aspect could be exploring Rook's past more deeply. Maybe he has some secrets from his time before being a Plumber that are related to the Ben 10 Omniverse. Ben could help him uncover these secrets while they are on a mission. For example, they could be investigating an ancient alien artifact, and as they dig deeper, Rook's past starts to unfold.
One great Ben 10 and Rook fanfiction is 'The Galactic Adventures'. It takes Ben and Rook on a journey across different galaxies to save the universe from a new and powerful threat. Another interesting one is 'Rook's Secret Mission'. In this story, Rook has to go on a solo mission while Ben is dealing with a local villain on Earth. It shows Rook's skills and his determination. And 'Ben and Rook: Partners Forever' is also a good read. It focuses on their friendship and how they grow as a team, facing various challenges together.
One good Ben and Rook lemon fanfiction could be 'A New Bond'. It focuses on the deepening relationship between Ben and Rook in a rather emotional and slightly romantic way, while still maintaining the essence of their friendship from the original series.
There could be a fanfiction where Fem Rook has to rescue Ben from a powerful enemy. In this story, Fem Rook would use her combat skills and strategic thinking to save the day. It could show how their relationship has grown over time and how much they rely on each other.
One possible fanfiction could be about Ben and Kai going on a new adventure in the Omniverse. Maybe they discover a new alien species that is causing chaos in a far - flung galaxy. Ben uses his Omnitrix to transform into different aliens to try and stop the threat, while Kai uses her martial arts skills to fight alongside him.
There probably is. Fanfiction communities are quite large and diverse. Try looking on platforms dedicated to the fandom that Ben and Rook are from. Some writers might have explored this relationship with a kiss scene in their stories.