Maybe Sasuke. Although they are rivals, they also have a deep bond. Sasuke might have come across a unique jutsu during his travels and decide to teach it to Naruto so that they can both become stronger and better protect their village.
It could be a new form of Rasengan. Maybe Naruto discovers a way to combine different elements with the Rasengan more effectively, like adding lightning to it for a more powerful and faster attack.
If Naruto has a new secret jutsu in fanfic, like a super - powerful healing jutsu, it could change the story by allowing him to save more lives during battles. For example, he could heal injured comrades immediately and keep them in the fight. This would boost the morale of his side and potentially change the outcome of many battles.
A third idea for a Naruto poison jutsu fanfic could be a story set in a different era of the Naruto universe. In this time, poison jutsu is a highly respected and feared art. A young ninja, inspired by tales of Naruto, tries to master poison jutsu. However, they face many challenges, including a corrupt master who wants to use the ninja's skills for evil. The young ninja must then decide whether to follow the master or break away and use their skills for the greater good.
One idea could be a fanfic where a young ninja discovers a unique way to combine lightning jutsu with other elements like water, creating a new and powerful technique. This could lead to him being sought after by different clans for his knowledge.
One interesting Naruto secret jutsu in fanfiction could be a time - traveling jutsu. It allows Naruto to go back in time and change certain events in the ninja world. This can lead to all kinds of new storylines and character developments.
He could practice in secret locations where no one can see him. For example, in an abandoned cave or a hidden part of the forest. That way, no one will know about the new jutsu he's developing.
Well, I remember a fanfic that focused on a side character getting the absorption jutsu. It was titled 'Sideways with Absorption'. The story details how this character, who was previously overlooked, suddenly becomes a key player in the village's defense with the help of this powerful jutsu. It also delves into the character's relationships with other Naruto characters and how they react to this newfound power.
I really like this fanfic. It often explores unique aspects of the Naruto universe that the original series might not have delved into deeply. For example, it could introduce new jutsu combinations or character developments that are quite refreshing. The way it continues from the first part usually means it builds on the existing plot and character relationships, which can be very engaging for fans who are already familiar with the initial story.