Ben and Kai are likely candidates. Ben is the hero with the Omnitrix, and Kai is his adventurous and tough - minded friend. Their dynamic of going through dangerous situations together could easily lead to a romantic relationship.
Another possibility could be Ben and Rook. Although they are more like best friends in the series, their deep friendship could potentially develop into something more. Rook's loyalty and his different way of looking at things compared to Ben could be the basis for a unique love story.
The main characters are Ben and Kai. Ben is a heroic figure with the Omnitrix, which is a device full of alien DNA that he can use to transform. He is brave and always ready to protect the Omniverse. Kai, on the other hand, is a feisty and determined character. She brings her own charm and abilities to the story. In a 'Ben 10 Omniverse Ben x Kai' fanfic, these two are the focus. Their different personalities clash and complement each other as they navigate the dangerous and exciting world of the Omniverse together.
The main characters are obviously Ben and Kai. Ben is the wielder of the Omnitrix, which gives him the power to transform into various alien forms. Kai is a strong - willed and adventurous character who often gets involved in Ben's escapades.
There's also a chance that it could be a former enemy of Ben who has a grudge. They might want to get revenge on Ben by kidnapping him and putting him in a difficult situation. It could also be a mad scientist who wants to study Ben's alien forms and the Omnitrix, so they kidnap him to do all sorts of experiments on him.
Ben is an obvious choice as he is the main character. His different alien forms offer a lot of possibilities for storylines. Gwen is also great as she has her own powers and a complex relationship with Ben. And of course, Kevin, with his unique abilities and his friendship - turned - rivalry - turned - friendship again with Ben.
In Ben 10 Omniverse, there could be a love story between Ben and Kai. They often go on adventures together. Kai is a strong and brave girl. Ben, with his Omnitrix, saves the day while Kai is always by his side. Their relationship grows as they face various challenges and enemies. The bond between them is special as they understand each other's strengths and weaknesses, and they share a mutual respect which could easily turn into a deep love.
Definitely Ben Tennyson himself. He's the main character and the one with the Omnitrix. His different alien forms like Heatblast, Four Arms, and XLR8 can add a lot of action and variety to the story.
Well, in a 'Ben 10 Omniverse Ben x Kai' fanfic, perhaps it could start with Kai joining Ben on one of his inter - dimensional adventures. Along the way, they encounter various challenges that test their relationship. Ben might use his Omnitrix in creative ways to protect Kai, and in the process, they realize their mutual attraction. For example, when they are trapped in a strange alien world, Ben has to transform into different aliens to find a way out while also keeping Kai safe from the local dangers.
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 possible plot could be that Esther gets caught up in an alien conspiracy in the Omniverse. Ben, being the hero, steps in to save her. As they work together to uncover the truth behind the conspiracy, they start to fall for each other.
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.