Perhaps Naruto, as Katanas' nephew, gets involved in a conflict that dates back to the family's past. For example, an old feud with another ninja clan. And he has to use his skills and new - found family knowledge to resolve it. He might also learn some special sword techniques from his family connection to Katanas.
Maybe it's a magical creature. For instance, a centaur could give it to Harry. Centaurs are known for their knowledge of magic and prophecies. They might believe that Harry is the one destined to have the three - bladed scythe to fulfill some important task in the wizarding world.
There could be a time - travel fanfic where a modern - day katana collector is transported back in time to an era when big cats were revered as gods. The collector must use their knowledge of the katana and form an alliance with the big cats to find a way back home.
There could also be a character within the village who is envious of Naruto's new family connection. This person might try to undermine Naruto at every turn, causing internal conflicts within the village as well as problems for Naruto personally.
One idea could be that Naruto discovers the lightsaber in a hidden ninja temple that has some sort of inter - dimensional portal. He then has to learn how to use it without any prior knowledge of lightsabers. It could be a comical journey as he tries to figure out how to hold it and not accidentally cut himself or his friends.
One idea could be that Naruto discovers the lightsaber in a hidden ancient temple during one of his adventures. He initially has trouble controlling it due to its unique dual - bladed nature, but with his determination and quick learning skills, he soon masters it and uses it to fend off powerful enemies. This new weapon gives him an edge in battles and also makes his combat style more diverse.
Maybe a group of big cats are magically given the ability to transform into human - like forms and they are trained in the art of the katana. They form a secret order that protects the forest from dark forces, using their feline instincts and katana skills.
In a fanfic where Naruto has a duel bladed lightsaber, he might have to learn new combat styles. The lightsaber requires a different form of handling compared to his usual ninja weapons. He could end up training with someone who has knowledge of lightsabers, perhaps a crossover character from the Star Wars universe. This would lead to some really cool training scenes where Naruto is learning to balance his ninja abilities with the new weapon. And his opponents would be in for a big surprise when they face him with this unexpected weapon.
Well, perhaps Harry could discover that the three - bladed scythe has some magical powers. It might be a weapon against a new dark force that he has to face. Maybe it was left behind by an ancient wizard and holds the key to unlocking a great mystery.
A possible plot could be that Naruto is sent on a special mission to a far - off planet where lightsabers are common. There, he is given a dual bladed lightsaber by a wise old Jedi - like figure. He then has to learn the ways of the lightsaber while also dealing with local politics and power struggles. Back on Earth, his enemies sense his new power and start plotting against him. Naruto must return in time to save his village, using the skills and power he gained from his adventure with the lightsaber.