Well, a really cool idea in such fanfiction could be the social implications of the expansion jutsu. Like how other villages view a ninja who has mastered this jutsu. Do they fear them? Or do they try to recruit them? And also, how does the ninja who can use it interact with their own village? Are they treated as a valuable asset or an outcast because of the power of their jutsu?
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.
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.
Perhaps in the fanfiction, Naruto perfects the Sexy Jutsu to the point where it can be used for espionage. He could transform into a seductive character and infiltrate enemy strongholds, gathering valuable information without being detected. This would add a new dimension to his ninja skills.
A cool Naruto Cheat Code Jutsu Fanfiction idea is a cheat code that unlocks ancient and lost jutsus. These jutsus could be super - powerful and have unique effects. Maybe a jutsu that can freeze time for a short period or a jutsu that can teleport across long distances without using chakra. Also, a cheat code that gives a character the ability to control the weather using jutsu would be really interesting.
A 'Solar - Flare Rasengan'. Naruto could combine his wind - style chakra with some kind of solar - based energy he discovers. This jutsu would be like a super - charged Rasengan that emits a blinding light as well as powerful wind - based damage.
A jutsu that allows the user to transform their chakra into a liquid form that can seep into the ground and then resurface anywhere within a certain radius as a surprise attack. Another could be a jutsu that uses sound waves to disrupt an opponent's chakra flow, like a high - pitched noise that throws off their concentration and ability to perform jutsus.
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.