Many characters would have interesting reactions. Tsunade would likely see it as an opportunity for Naruto to grow and diversify his skills. She might allocate some resources for his sword training. Jiraiya, if he were still alive, would probably be proud and see it as another step in Naruto's journey to become a great ninja. Gaara might view it as a sign of Naruto's ever - expanding power and be even more determined to keep up with him in terms of strength. And the Akatsuki members, if they knew, would probably start to re - evaluate Naruto as a more serious threat now that he has a new and dangerous weapon at his disposal.
One possible consequence could be that Naruto gains a new and powerful weapon. This sword might have unique abilities that could enhance his combat skills. He could use it to intimidate his enemies or as a last - resort weapon when his regular jutsu are ineffective.
Maybe he defeated Zabuza in a battle and took it as a trophy.
On a more practical level, Naruto's skills might be misused. Instead of using his power to protect Konoha and the people he cares about, he's using it for Zabuza's self - centered motives. This could also make him a target for other ninja who oppose Zabuza. So not only is he in danger from the people he used to call friends, but also from new enemies. And if he ever tries to break free from Zabuza, he might face severe retaliation from Zabuza himself, which could be life - threatening.
Hinata would be heartbroken. She loves Naruto deeply. Her world would shatter. She might try to find out the truth behind his death, not believing that his friends could do such a thing without a good reason. And she would probably hold a grudge against those involved.
Sakura might be a bit annoyed at first. She's used to Naruto being independent and always charging forward, and Gaara's overprotectiveness could seem like it's getting in the way. Kakashi, on the other hand, would probably be more understanding. He'd see the value in Naruto having someone looking out for him, but he might also try to encourage Gaara to let Naruto grow on his own a bit. Sasuke could have a very negative reaction. He might see it as Gaara trying to steal Naruto away from him in a sense, especially if he has his own unresolved feelings towards Naruto.
Well, one possibility is that Naruto gets Zabuza's sword and tries to master its use. He might face challenges in understanding the unique abilities of the sword. Maybe he initially struggles to wield it properly because it's a different type of weapon compared to his usual ninja tools. But as he trains with it, he discovers new fighting techniques and becomes more powerful.
Sasuke would likely be enraged. He and Naruto had a complex relationship, and Naruto was like a brother to him. He would probably seek revenge on Sakura immediately. Kakashi, as their teacher, would be deeply shocked and disappointed. He might struggle to understand how Sakura could do such a thing. The villagers would also be in turmoil. Naruto was their hero, and his death at Sakura's hands would cause a great deal of confusion and anger among them.
Sakura might be really shocked. She always saw Naruto as a friend and a fellow ninja, and this would be a completely unexpected development. She might be a bit confused about how this would change their relationships. Sasuke, on the other hand, might be more indifferent on the surface but secretly curious. Kakashi would probably be very concerned. He's always been like a mentor to Naruto, and this situation would raise a lot of questions for him about Naruto's future and how this would affect the village. And the elders of the village would likely be in an uproar. They are always worried about the stability of the village, and this would be a huge bombshell that could disrupt the village's order.
A minor character like a blacksmith's apprentice could find Zabuza's sword. Instead of using it for fighting, they study it closely. They discover a unique metal alloy in the sword that they use to create new and improved weapons for their village. This not only changes their own fate as they become a renowned blacksmith, but also the fate of the village as they now have better weapons to defend themselves.
His fighting style would likely become more melee - focused. Naruto is used to fighting from a distance with his jutsu, but with Zabuza's sword, he would need to get up close and personal. He might start to combine his ninjutsu with sword strikes. For example, he could use a clone to distract an enemy while he closes in with the sword for a surprise attack.