It could be a water - based kekkei genkai. Since the Wave arc has a lot to do with water, it would make sense for Naruto to awaken a kekkei genkai related to water. This could give him an edge in battles, especially in the Wave region where water is abundant.
Another aspect could be a fanfiction set in an alternate universe where Genkai and Younger Toguro are allies against a greater evil. They could use their combined skills and knowledge to fight off powerful demons. This would show a different side of their relationship, more of a partnership than what we might expect from their normal interactions in the original series.
Having a kekkei genkai in fanfiction could completely transform Naruto's journey. It might unlock hidden potential within him, affect his relationships with other characters, and introduce new conflicts and resolutions that weren't present in the original storyline.
In some fanfiction, they could be involved in a tournament together. Genkai as a mentor figure guiding Younger Toguro through the challenges of the tournament, teaching him strategies and how to control his emotions during the battles. This would show their relationship evolving in a high - stress environment.
Typically, it might involve elements related to the sakura, such as its beauty or symbolism, combined with the idea of a kekkai genkai which is often a special ability or power in certain fictional universes. So there could be a character with a unique power related to sakura.
To integrate the Uzumaki clan's kekkei genkai into a new story line, consider creating a mystery around it. The main character could start off not knowing they have this kekkei genkai, but they keep experiencing strange events. As they investigate, they find out about their Uzumaki heritage and the kekkei genkai. They then have to figure out how to use it to solve the mystery of an ancient evil that is related to their clan. You can also have the kekkei genkai be a key factor in a tournament or competition. The Uzumaki character has to use their kekkei genkai in creative ways to win and prove the worth of their clan.
One interesting concept could be exploring an unknown kekkei genkai of the Uzumaki clan that gives them the ability to manipulate time on a small scale. For example, they could slow down time for a brief moment in battle, giving them an edge. Another idea is a kekkei genkai that allows them to communicate with the spirits of their ancestors, gaining wisdom and power from them. Maybe a kekkei genkai that lets them transform into a powerful beast form related to their clan symbol.
His relationship with Sasuke might become more competitive. If Naruto awakens a powerful kekkei genkai, Sasuke, who is always striving to be stronger, would see Naruto as an even greater rival. This could lead to more intense training sessions between them and also some tension in their friendship.
The main themes might include transformation and evolution. Starting from 'genkai level 1', the story could be about how the protagonist changes and develops over time. There may also be themes related to exploration, as they move from this initial state to something greater. And also, perseverance could be a theme, as rising up usually requires the character to keep going in the face of difficulties.