In certain fanfiction concepts, Naruto is given the Sword of Tengu by a powerful ally. This ally might recognize Naruto's potential and see him as the rightful wielder of the sword. They give it to him to aid in his fight against the common enemies, such as the Akatsuki or other powerful villains in the Naruto universe. The sword might then have special powers that Naruto has to learn to master, which could be a major part of the fanfiction's plot.
Well, in some fanfictions, Naruto might obtain the Sword of Tengu through a quest. Maybe he has to help a spirit or an ancient being in return for the sword.
One possible ability could be enhanced cutting power. It might be able to cut through almost any material, even chakra - based defenses with ease.
Well, in some fanfictions, Naruto might obtain the overpowered sword through a mysterious inheritance. Maybe it was left by a powerful ninja from the past and Naruto discovers it in a hidden cave or something.
Well, in some fanfictions, Naruto might obtain the Master Sword through a strange portal that connects his world to the world where the Master Sword exists. Maybe he's on a mission and stumbles upon it by accident.
In some fanfictions, Naruto might obtain the dragon sword through a special quest. Maybe he stumbles upon an ancient temple during one of his missions where the sword is hidden as a powerful artifact, guarded by some kind of magic or traps. He overcomes these obstacles using his ninja skills and determination, and thus gets the dragon sword.
One idea could be that the Sword of Tengu has a hidden power that only the protagonist can unlock. This power could be related to an ancient jutsu that was sealed within the sword long ago. Another idea is that the sword has a spirit that communicates with the wielder, guiding them in their battles and adventures in the Naruto world.
Naruto himself could be a great main character. Imagine Naruto finding the Sword of Tengu during one of his adventures. He could struggle at first to understand the sword's power, but with his determination, he would eventually master it and use it to protect the village in a new and exciting way.
Well, in some fanfictions, he might inherit it from an unknown ninja clan. Maybe his parents left it for him and it was hidden until he discovers his true heritage.
In some fanfictions, Naruto might obtain Cloud's sword through a series of adventures. Maybe he helps the Cloud Village in a great battle and as a reward, he is given the sword. Or perhaps he discovers it during an exploration of an ancient ruin that has a connection to the Cloud Village's history.
In many fanfictions, Naruto might obtain the Uzumaki sword through a hidden inheritance. Maybe it was left behind by an ancient Uzumaki clan member and Naruto discovers it in a secret location, like an old, forgotten Uzumaki shrine.
He could discover it during a dangerous mission in an ancient ruin. Maybe he was exploring an old ninja stronghold and came across the sword hidden away. It might have been protected by traps and guardians, which he had to overcome to obtain it.