One idea could be a story where Naruto discovers a new, ancient space - time jutsu that allows him to travel to alternate universes. In these universes, he meets different versions of his friends and enemies, and has to find a way to return home while also dealing with the chaos caused by the jutsu's power.
Another plot could involve Naruto using a space - time jutsu to go back in time and prevent a great tragedy from happening in the Hidden Leaf Village. However, by changing the past, he unknowingly creates new problems in the present. He then has to use his wits and the knowledge he gained from the future to fix the new issues and restore balance.
Maybe in the fanfiction, an enemy uses a powerful space - time jutsu to trap Naruto and his team in a time - loop. Each time they try to break free, they face new challenges and have to figure out the true nature of the jutsu in order to escape for good. They also learn more about themselves and their relationships during each loop.
Well, perhaps a plot where the harem no jutsu is used not just for comical effect but to actually solve a complex political situation in the Naruto world. The various characters in the 'harem' could use their unique skills and influence to bring about peace. It could also be interesting to see how Naruto manages this new dynamic among the characters in his 'harem' and how it changes his relationships with them on a deeper level.
Here's a cool idea. In a 'Naruto Shadow Possession Jutsu Fanfiction', the jutsu could be passed down through generations in a family, but with a curse. Every time it's used, it slowly drains the user's life force. A young heir of this family has to find a way to break the curse while still using the jutsu to protect their loved ones. Another plot could be that an enemy uses the Shadow Possession Jutsu to create an army of shadow - controlled puppets. Naruto and his team must find a way to stop this without harming the people who are being controlled. And then there could be a story where the jutsu is combined with a new type of chakra, creating a whole new set of abilities that the main character has to master.
One idea could be that Naruto accidentally uses the Reverse Harem Jutsu on himself instead of an opponent. He then has to deal with the chaos of multiple versions of himself with different personalities. For example, one might be super confident, another shy, and they all have to work together to solve a problem in the village.
One idea could be a story where the main character uses Oriko Jutsu in a unique way to communicate with the Kyuubi. Maybe they form an unexpected alliance to face a new, powerful enemy in the Naruto universe.
One interesting idea could be exploring new and unique ways the expansion jutsu can be used in battles. For example, using it not just for physical size increase but also for expanding the range of other jutsus.
Some fanfictions might explore the idea of combining Forbidden Jutsus. Picture a scenario where a rogue ninja combines a Forbidden Jutsu of destruction with a Forbidden Jutsu of mind control. This could create a super - powerful and extremely dangerous new ability, and the story could follow the efforts of the main characters to stop this new threat.
One interesting idea could be the reanimation of minor characters from the Naruto series and exploring their backstories that were not fully told in the original. For example, reanimating a random shinobi from a minor clan and showing how their clan's unique abilities could have been used more effectively in the war. Another idea might be the reanimation of characters from different time periods in the Naruto universe's history, like shinobi from the era before the Hidden Villages were established.
One idea could be a story where Naruto uses the Saimin Jutsu in a creative way during a crucial battle. Maybe he uses it to make the enemy see illusions of their worst fears, causing them to be paralyzed with fear and unable to fight back effectively.
One idea could be a fanfic where Naruto discovers a new and powerful summon that no one has ever seen before. This summon could have unique abilities that help Naruto in a crucial battle against a powerful enemy.
They could study ancient scrolls. In the Naruto world, there are often hidden scrolls with powerful jutsu. A character might stumble upon one that has the secrets of a new space - time jutsu. By deciphering the symbols and practicing the techniques described, they could develop the new jutsu.