Well, it could be that the sword was lost and Naruto stumbles upon it by accident. He then realizes its significance and decides to keep it, learning to use it in his own unique way. Another possibility is that the sword is given to him by a character from the Cloud Village who sees great potential in Naruto and believes he can use the sword for good.
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 fanfiction, the sword could have a spiritual power. It might be able to communicate with Naruto on a spiritual level, guiding him in battles or revealing secrets about the past. It could also have the power to create illusions specific to the Cloud Village's history or mythology, confusing enemies and giving Naruto an advantage in combat.
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.
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.
Well, in some fanfictions, Naruto might defeat Kisame in a battle and take the sword as a trophy. Maybe he uses his newfound Sage Mode powers or some other advanced jutsu to overpower Kisame and claim the sword.
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.
Well, he might obtain it in a fight. Maybe after defeating an enemy who had stolen Zabuza's sword from its original place. Or perhaps he discovers it in an old, forgotten hideout where Zabuza once stashed his things.
Maybe he defeated Zabuza in a battle and took it as a trophy.
Maybe he finds it in an old family vault that was hidden away.