One possible plot twist could be that during their training, they accidentally discover a new and powerful jutsu. Maybe it's a jutsu that combines their unique abilities. Naruto's chakra control could be enhanced by Hinata's gentle fist style in an unexpected way, leading to a whole new form of attack or defense.
Well, perhaps a plot twist could be that an old enemy resurfaces but this time they target Hinata to get to Naruto. This forces Naruto to not only protect his new wife but also figure out why this enemy is after her specifically. It could also add a layer of drama if Hinata decides to take matters into her own hands and train secretly to be able to defend herself and Naruto better. Or, there could be a political plot twist where their marriage causes unrest in the ninja world because of Hinata's family status and Naruto's position as a hero, leading to them having to fight against those who oppose their union.
A plot twist could be that Sakura and Hinata actually team up against Naruto in some way. Perhaps they realize that Naruto is being pushed into a relationship by the village elders for political reasons. So, they decide to fake a relationship between themselves to make Naruto see that he should be free to choose his own path and not be pressured into a marriage. This would turn the typical love triangle on its head.
One possible plot twist could be that Orochimaru has an ulterior motive for training Sakura. Maybe he wants to use her new - found skills against Konoha in the future. Another could be that Sakura discovers a hidden power within herself during the training that Orochimaru wasn't expecting.
The plot might involve Naruto and Ino training together for a big upcoming battle. Ino could be helping Naruto with his sensory skills while Naruto helps her with her strength training. They might also have some friendly competitions during the training, which not only make the training more fun but also help them discover new abilities within themselves. And in the end, they become a stronger team ready to face any threat.
One possible plot twist could be that Naruto and Hinata have to quickly learn to control their newfound Jinchuuriki powers. Maybe they are suddenly thrust into a situation where an ancient evil is awakened and only their combined Jinchuuriki abilities can stop it. For example, they might discover that there is a hidden prophecy about two Jinchuuriki working together to save the world.
One possible plot twist could be that an old enemy resurfaces just as they are about to get engaged. This enemy might try to disrupt their relationship by spreading false rumors about Naruto, like he has some hidden dark power that could endanger Hinata. Another twist could be that Hinata's family has some ancient clan secret that surfaces and creates a rift between them and Naruto's side. Maybe the secret is related to a power that the Hyuga clan once had and lost, and they fear Naruto might be involved in its re - emergence in a negative way.
In a Naruto trains Hanabi fanfic, the plot could be centered on Naruto introducing Hanabi to new elements of ninja life. Since Naruto has interacted with various ninja from different villages, he could expose Hanabi to different fighting styles and strategies. He might take her on a journey to different training grounds, where she can learn from the environment and face new challenges. This could also lead to Hanabi developing new friendships and alliances, all while becoming a stronger ninja under Naruto's guidance.
One possible plot could be that Naruto and Gohan start training together. Naruto is amazed by Gohan's Saiyan power and Gohan is intrigued by Naruto's ninja skills. They exchange techniques, like Naruto showing Gohan how to use shadow clones for training efficiency and Gohan teaching Naruto how to sense and control his ki. Eventually, they team up to face a common enemy that threatens both their worlds.
One possible plot twist could be that Naruto discovers a secret conspiracy against Hinata's family while being her bodyguard. Maybe the real threat is not from an obvious enemy but from within the village's own political circles. He then has to protect Hinata not just from physical harm but also from being used as a pawn in this political game.
Maybe Naruto finds out that there are some English magic users who mistake him for a powerful wizard due to his chakra abilities. This misunderstanding could create some really interesting and comical situations, like when they try to enroll him in their magic school and he has to explain his ninja powers.