Well, in the Naruto universe, for Naruto to make a Treant Jutsu, he might first need to study nature chakra deeply. He could observe how trees grow and thrive, and then try to infuse his own chakra with the essence of nature. Maybe he'd have to combine his shadow clone jutsu in a new way, having clones study different aspects of trees, like their root systems and how they absorb nutrients. Then he could use his Rasengan as a base and add the nature - based tree - like elements to it, gradually forming a Treant - like structure out of his chakra.
The Treant could have the ability to absorb and store chakra from the environment. Just like real trees absorb sunlight and nutrients, this Treant made by Naruto could soak up ambient chakra, making it stronger over time. It could also use its branches to perform long - range attacks, similar to how a ninja would use kunai or shuriken. And, it might be able to camouflage itself as a normal tree in the forest, giving Naruto an element of surprise in battle.
One possibility could be that Naruto discovers a hidden ability within himself to use Wood - Style Treant Jutsu. Maybe he unlocks it during a life - threatening battle where he needs to protect his friends. He could combine his own chakra with some ancient energy source in the forest to create these powerful treant - like creatures that fight on his side.
The fanfic could start with Naruto having a strange dream about using Wood - Style Treant Jutsu. He wakes up curious and starts to experiment. He finds that he can transfer his own emotions into the treants, making them more aggressive or defensive depending on how he feels. As he gets better at it, he uses the jutsu in a major battle against a group of rogue ninjas who are terrorizing a village. His treants become a symbol of hope for the villagers as they fight off the invaders.
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.
Well, in fanfic, anything can happen. Naruto is known for his creativity and adaptability. Maybe he discovers a new chakra - based metal - forging technique. He could combine his Rasengan's spinning energy with some sort of metal - shaping jutsu to mold the sword.
It could be that Naruto finds a way to reverse time in a small area. This would require an extremely powerful and dangerous technique. He might have to sacrifice something in return, like some of his own memories or a part of his chakra permanently. But if he manages to do it, he could go back to the time when Mito Uzumaki was still alive and bring her forward to the present.
It could be a complex plot where Naruto, disillusioned with the shinobi world for some reason, decides to create a new identity as the Masked Man. He might have seen too much corruption or pain and believes that by operating from the shadows as the Masked Man, he can bring about real change. He could be using the mask as a symbol to strike fear into those who are causing harm, while also trying to protect the ones he loves without them knowing it's actually him.
One way this could work is if there was a shared ancestry that was hidden or lost over time. Perhaps there was an ancient clan that had members in both the Naruto world and the Fairy Tail world. Through some convoluted plot device in the fanfic, Naruto and Erza could be discovered to be part of this long - forgotten clan, thus making them siblings.
In fanfiction, anything can be possible. Maybe some alternate universe scenario was created where Naruto and Yugito met under different circumstances. For example, if there were different political alliances in the ninja world that brought their two villages closer together. This could have led to more interactions between them and eventually a relationship that resulted in a daughter.
Well, in a really dark and twisted fanfiction, Sasuke could be under some sort of mind - control spell. The spell could be so strong that it overrides his feelings for Naruto. He might then attack and kill Naruto without fully realizing what he's doing. But in the real Naruto lore, their friendship and mutual respect are so strong that this is highly unlikely.