One plot twist could be that the marriage between Naruto and the demon is part of a prophecy. However, the prophecy is misinterpreted by most. As the story unfolds, they realize that the real purpose of their union is not what everyone thought, and it actually has the power to either save or destroy the ninja world. This would completely change the direction of the story and force the characters to re - evaluate their beliefs and actions.
A possible plot twist could be that the demon Naruto marries is actually a reincarnation of an ancient and powerful being, which brings a whole new level of danger and mystery to the story.
Another plot twist could be that Naruto's own chakra has an unexpected effect on the vampire. Perhaps it changes the vampire in some way, either making them more powerful or causing some sort of internal struggle within them. This would then have a big impact on their relationship as they both have to figure out how to deal with this new situation.
A plot twist could also be that Temari discovers a long - lost relative who has a dark past and tries to use Naruto's influence for evil purposes. Temari would be torn between family loyalty and her love for Naruto, and Naruto would have to help her make the right decision while also protecting their relationship and the villages.
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.
One interesting plot twist could be that Severus and Harry are forced to marry for political reasons in the wizarding world. Maybe there's a threat from a dark force and their union is seen as a way to unite different factions. Another could be that they initially hate the idea but gradually fall in love as they discover things about each other they never knew. For example, Harry might learn about Severus's deep - seated loyalty to Dumbledore and Severus might see Harry's strength beyond his Gryffindor bravado.
There is a fanfiction where Naruto marries a demon named Kyuubi. It delves into the idea of Naruto having to understand and co - exist with the demon on a much deeper level than just being a jinchuriki. The story may show how their relationship affects the village, his friends, and his overall journey as a ninja.
One plot twist might be that Aphrodite loses her powers when she falls in love with Naruto. This would change their relationship dynamic as she has to rely on Naruto in ways she never expected. Also, there could be a twist where a prophecy in Naruto's world predicts that his union with Aphrodite will either save or destroy both their worlds, and they have to figure out which it will be.
A possible plot twist could be that Naruto discovers he has a hidden connection to Smaug. Maybe he is related to Smaug in some long - lost magical way. Another twist could be that Smaug is not really a villain in this fanfiction. Instead, he is being controlled by a greater evil, and Naruto has to figure out how to free Smaug from this control. It would change the whole dynamic of their relationship from one of enmity to a more complex situation where they could potentially become allies.
A possible plot twist could be that Naruto turns out to be a keyblade wielder in disguise. This would completely change the dynamic as everyone in the Naruto world and Kairi would be shocked. It could also mean that Naruto has a whole different origin and mission related to the world of Kingdom Hearts.
A possible plot twist could be that one of the Autobots is actually being controlled by an old enemy from Naruto's world. This enemy has found a way to hack into the Autobot's system and use it for their own revenge. So, while the Autobots seem to be helping Naruto, in reality, they might be leading him into a trap.
One plot idea could be that Naruto, after achieving great peace in the ninja world, decides to settle down. Tsunade, who has seen Naruto grow from a young boy to a great hero, realizes her feelings for him. Shizune, having been by Tsunade's side all along, also develops feelings. They all decide to form an unconventional family. Naruto's ability to bring people together and his unwavering spirit could be central to this plot.