Maybe the secret fiance was sent from the future to change Naruto's fate. So she engaged to him secretly to make sure he doesn't make certain mistakes in the future battles. This would add a time - travel element to the fanfiction and completely change the expected plot.
It could be that the secret fiance is a clone of someone Naruto loves. The real person is held captive, and the clone was created to deceive Naruto. When Naruto discovers this, he has to find a way to save the real person and deal with the emotional turmoil of being deceived by the clone.
A possible plot twist could be that his secret fiance is actually an enemy in disguise. She got close to Naruto under false pretenses, and as the story unfolds, Naruto has to deal with the betrayal and the fact that his feelings were used against him.
It could be Hinata. In the original series, Hinata has a deep affection for Naruto. In a fanfiction, it would be a natural progression for her to be his secret fiance. Maybe they got engaged secretly to avoid some political unrest in the village.
I'm not sure which specific 'False Fiance Secret Story' you are referring to. There could be many stories with such a title or concept. It could be about someone who pretended to be a fiance for some ulterior motives, like financial gain or to deceive family and friends.
Another plot could be that the false fiance is part of a revenge plan against the main character or their family. By getting close as a fiance, they can execute their plan more effectively, like causing a rift in the family or ruining the main character's reputation. The story would be full of twists and turns as the real intentions are gradually uncovered.
Naruto and Rias are the central characters. Naruto is known for his never - give - up attitude and his array of ninja techniques. Rias is a complex character with her own political and social standing in the devil world. However, in some fanfictions, other characters from both the Naruto and High School DxD universes can become important. Kiba from Naruto might befriend Naruto in the new world and help him understand the devil society better. And from the High School DxD side, Akeno, Rias' friend, could play a role in either supporting or testing Naruto's relationship with Rias.
A common plot in Naruto Rias Fiance fanfiction is the power - up journey of Naruto. As he is now in a new environment with different power systems, he has to level up. He could gain new devil - related powers through his connection with Rias. Also, there could be a plot about their relationship development. How they overcome misunderstandings and cultural differences. For instance, Naruto's straightforward ninja way might clash with the more complex and often secretive devil society, and how they resolve these issues can be an exciting part of the story.
It might also be Gaara. Their initial encounters were filled with tension, but as the story could be twisted in fanfiction, that could develop into a different kind of relationship. Gaara's own journey of self - discovery and Naruto's influence on him could be a basis for a romantic relationship in fanfic.
One possible plot could be that Naruto discovers he has a child during a mission. Maybe he saved a village years ago and unknowingly had a relationship with a local woman. The child could be in danger from some villains who want to use the child's connection to Naruto for their own evil plans.
Well, perhaps the story could be about Naruto finding out he has a sister who was hidden away for her own safety. Maybe she has some unique powers that the villains are after, and Naruto has to protect her while also learning about his family's past.
His son could inherit Naruto's powerful chakra and the ability to use the Rasengan. Maybe also have some form of enhanced speed and strength like Naruto. After all, Naruto's powers are quite dominant.
Enemies from Naruto's past or Sona's enemies could target them as a couple. Since Naruto has made many foes during his adventures, and Sona may also have her own enemies, their engagement could put a target on their backs.