There could be a rival character, a fellow ninja who is jealous of the seal master's skills with the Hiraishin. This rival might constantly try to undermine the seal master or steal their techniques, adding a layer of conflict to the story.
One interesting plotline could be the main character, as a seal master, using the Hiraishin in unique ways to solve difficult battles. For example, creating new seals that combine the power of the Hiraishin with other jutsu.
The plot might revolve around a threat to the village. Naruto, with his seal master skills and Hiraishin, is at the forefront of defense. Hinata, who has always admired Naruto's strength, decides to train harder under his guidance. As they work together, they start to develop deeper feelings for each other. Naruto could use his seal knowledge to create a special protection seal around Hinata during battles, showing his care for her.
Their relationship could start with Hinata's admiration for Naruto's newfound skills as a seal master. Naruto, being focused on his Hiraishin research, might not notice Hinata's feelings at first. But as she offers her support and assistance, he starts to see her in a new light. Eventually, they could become closer as they share their thoughts and experiences related to the seals and the Hiraishin.
It could lead to some really interesting plot twists. Naruto's new ability as a seal master might give him an edge in battles and change the dynamics of his relationships with other characters.
It could be a rogue ninja who was once a student of the Hiraishin master but turned evil. They might have a twisted view of the technique and use it for their own selfish and harmful purposes, like stealing important artifacts from different villages.
Naruto's life would be very different. He would be more respected in the ninja world for his unique skills. Instead of just being known for his Nine - Tails chakra, his sealing abilities would also be a major factor. He could use his sealing skills to protect the village in new ways, like creating powerful seals around Konoha to prevent enemy attacks. Also, he might be called upon more often to deal with dangerous artifacts or threats that require sealing.
Perhaps the story could focus on a character who is not Naruto becoming a Hiraishin master. They could struggle to be accepted in the ninja world because they're not from the Uzumaki clan but still manage to prove their worth with unique applications of the technique. For example, using it in combination with other elemental jutsus in ways no one has thought of before.
Writers often start by giving the Seal Master Anbu a distinct backstory. Maybe he learned sealing arts from a reclusive master or had a family with a history of sealing. This gives depth to the character.
In terms of character design, as a seal master, she would likely have a unique appearance. Maybe she has tattoos or markings related to sealing on her body. Her personality could be very studious and detail - oriented, given the complexity of seals. She would also need to be strong - willed, as dealing with the power of seals requires a great deal of self - control. Her presence in the fanfiction could attract other characters interested in seals, creating a community within the story.