The sword might be able to enhance Naruto's existing jutsus. For example, his Rasengan could become more powerful when combined with the sword's energy. It could also give him new elemental powers, like the ability to control lightning or fire in a different way than before.
One really interesting ability could be that the sword can create illusions. Naruto is not that great with genjutsu, but with the sword, he could use powerful illusions to deceive his enemies. It could also have a healing ability. When Naruto is injured in battle, the sword could emit a special energy that heals his wounds, making him more durable in combat.
It could be an old ninja who sees Naruto's potential. This ninja might have left the sword as a way to help Naruto in his future battles.
The Uzumaki sword might have the power of sealing. The Uzumaki clan was known for their sealing techniques. So, it's possible that the sword can be used to seal away powerful enemies or even seal away dangerous jutsu. It could also have the ability to cut through powerful defenses. Maybe it has some sort of special chakra edge that can break through barriers that are otherwise difficult to penetrate. Additionally, it could have a connection to the Uzumaki's life - force, allowing Naruto to draw on some of that power in times of need.
Well, he might discover that the sword has some special powers. Maybe it can cut through any material, or it could have the ability to absorb chakra. He could start training with it to become even stronger in battle.
The sword might also have a connection to the spirit world. It could allow Naruto to communicate with the spirits of the Uzumaki clan or gain insights from their past. This would give him an edge in battles as he could learn from the experiences of his ancestors.
Maybe the dragon sword has the ability to absorb chakra. When Naruto is in a fight, he could use this to his advantage by draining his opponents' chakra through the sword when it makes contact. This would weaken his enemies and at the same time, the absorbed chakra could be used to power up the sword's other abilities.
One possible ability could be enhanced cutting power. It might be able to cut through almost any material, even chakra - based defenses with ease.
In a 'Naruto Finds a Legendary Sword' fanfiction, a lot can happen. The sword might have a connection to Naruto's family. It could be a heirloom that was lost generations ago. This discovery could lead to Naruto learning more about his family's past and his own heritage. He may also have to go on a quest to fully understand the sword's powers and how to use them. He might meet new allies along the way who help him in his journey. There could be epic battles against those who want to steal the sword from him, and Naruto would have to use his wits and newfound sword skills to defend it.
He might start training with it. Naruto is always eager to improve his skills, and a new sword could be a great addition to his combat abilities.
One possible ability could be enhanced cutting power. It can slice through the toughest of materials, like it's cutting through butter. For example, it could easily cut through solid rock or even chakra - enhanced defenses.
The sword could have the ability to cut through any chakra - based attacks. Since Naruto's world is full of ninjas using chakra, this would be a very useful ability. It would allow Naruto to easily defend against and counter his opponents' attacks.