One possible plot could be Naruto discovers the Samaheada in a hidden ancient shrine during one of his solo adventures. He initially struggles to control its power but with the help of Kakashi's guidance and some self - discovery, he gradually masters it and uses it to fend off a new, powerful enemy threatening the Hidden Leaf Village.
Another possibility is a new character created specifically for the fanfic. This antagonist could be a dark - chakra user who believes that the Samaheada's power should be used to reshape the ninja world according to his own twisted vision. He would view Naruto as a threat not only because he wields the Samaheada but also because of Naruto's reputation for bringing hope and change to the village.
Maybe it's an old and experienced Jedi master. They have the wisdom and skill to handle such a powerful weapon. They could have been on a long journey to find this 'best sword' and now use it to protect the galaxy from the rising dark side forces. They know all the secrets and techniques to fully utilize the power of this special lightsaber.
Definitely. There's a fanfic where the black blade allows Naruto to access a special chakra mode. This mode not only makes him stronger but also gives him the ability to sense his enemies' moves before they make them. It's a really cool power - up and changes the dynamic of his battles. In this fanfic, the black blade is like a key to unlocking Naruto's hidden potential.
Mystery is also a common theme. The origin of the dragon blade, its true powers, and its connection to the Naruto universe are usually shrouded in mystery. Writers like to explore these mysteries in their fanfics.
One possible plot could be Sakura using the kubikiribocho to defend her village or friends. She might face powerful enemies and have to master the weapon quickly.
A unique feature is the combination of two different universes. Naruto's ninja abilities like shadow clones and rasengan blend with Unlimited Blade Works' concept of noble phantasms.
One idea could be exploring the origin of the Totsuka Blade in the Naruto universe more deeply. Maybe it was created by an ancient clan with a special connection to the afterlife. Another idea is to have a character other than Itachi use the blade in a completely different way, like a young ninja who discovers its power accidentally.
Perhaps in the 'black blade naruto fanfic', the black blade has a connection to an ancient and forgotten clan. Naruto, being the main character, then delves into the history of this clan, uncovers secrets, and uses the knowledge and power associated with the blade to protect the Hidden Leaf Village from a looming threat that only he with the black blade can face.