A plot idea could be that the ninja's mouth is the key to unlocking a hidden dimension. Inside this dimension are powerful chakra sources that can enhance his abilities. But to get there, he has to solve a series of riddles and challenges that are related to his own past and the history of his clan. He teams up with his friends to figure out the mystery of his mouth and the hidden dimension.
Perhaps the ninja has a mouth that can transform into different shapes. This gives him the ability to mimic other people's voices perfectly. He gets involved in a mystery where he has to use this ability to deceive the enemy and gather intelligence. He has to be careful though, as if he's caught, it could mean the end for him and his team.
One possible fanfiction could be about a Naruto ninja who has a special mouth technique. Maybe it allows him to speak different languages and he uses this ability to communicate with various enemies and allies during a mission. He could be on a quest to find an ancient scroll that holds the secrets to enhancing his mouth - related jutsu.
One popular plot idea is a masked ninja being a long - lost relative of a main character. For example, they could be related to Naruto and have been in hiding all this time. Another idea is a masked ninja being a spy from another village, with a complex backstory of loyalty and betrayal. Also, there could be a masked ninja who is a time - traveler, coming from the future to change key events in the Naruto universe.
One idea could be a rogue ninja who was once a close friend of Naruto but turned due to a misunderstanding. They could have unique powers and be on a mission to prove their own version of justice.
A cool plot could be that an ice ninja has the power to freeze time within ice. The Akatsuki wants to capture this ninja to use their power for their own evil plans. Naruto and his team must protect the ice ninja and figure out a way to stop the Akatsuki from getting their hands on this dangerous ability.
One idea could be a story where the Ninja Wire is used in a new and unexpected way during a major battle. For example, the characters could use it to create complex traps that not only ensnare enemies but also redirect attacks. Another plot could revolve around a young ninja who discovers a unique property of the Ninja Wire and has to keep it a secret while trying to master it.
One idea could be a story where a medical ninja discovers a new healing jutsu during a difficult mission and has to protect the knowledge from enemy ninjas. Another could be about a medical ninja who uses their skills to heal a long - forgotten and powerful ninja, who then becomes an ally. Or perhaps a story of a medical ninja training under Tsunade to become the best in the village.
One idea could be a story about a young ninja from the Leaf Village who discovers a long - lost jutsu. This jutsu gives them unique powers that no one else has, and they have to learn to control it while facing off against enemies who want to steal it for themselves.
One idea could be a story about a new student at the ninja academy who has a unique and secret jutsu that no one else knows about. This student tries to keep it hidden while also trying to fit in with the other students like Naruto and Sasuke.
A great plot for 'naruto as guardian ninja fanfiction' could be Naruto becoming the guardian of a group of young orphans who have special ninja abilities. These orphans are being targeted by an evil organization that wants to use their powers for bad. Naruto has to protect them, train them, and at the same time, keep their existence a secret from the world. He would have to deal with the emotional trauma of the orphans and help them grow into strong and kind - hearted ninjas.
One idea could be a trial where Naruto is wrongly accused of a crime he didn't commit, and he has to prove his innocence while facing his own friends' doubts. Another could be a ninja tribunal that is secretly being manipulated by an enemy to frame various shinobi.