If Naruto had the gura gura fruit in a fanfiction, his character would change in several ways. His confidence might grow even more as he realizes the potential of this new power. However, he would also face new moral dilemmas. For instance, he has always been about protecting his friends and the village, but the gura gura fruit's power is so great that he could potentially cause harm to innocent people if he's not extremely careful. So he would have to be more self - reflective and learn to control his impulses better. Also, he might become a target for more powerful enemies who want to either steal the fruit or eliminate him to prevent him from becoming too strong.
Naruto would become more powerful, and this might make him a bit more cautious. He's used to his regular ninja abilities, but the gura gura fruit's power is on a different level. He might be more hesitant in battles at first, not wanting to accidentally cause too much destruction with the fruit's earthquake - causing ability.
Naruto's character would change quite a bit. Firstly, he would be more aware of his new - found strength. The gura gura fruit gives him the ability to create massive destruction, which is different from his usual ninjutsu. This could make him more serious in some ways. He would also need to adapt his fighting style. Instead of relying solely on his shadow clones and Rasengan, he would have to incorporate the power of the gura gura fruit. And since the power is so unique, he might start to see the world of ninjas in a different light, realizing that there are powers out there that are far beyond what he has known. He might also become more of a loner at times, as he tries to master the fruit's power without endangering his friends.
In a fanfiction about Naruto, the Gura Gura Fruit, and the Third Shinobi War, perhaps the Gura Gura Fruit is a new, mysterious element introduced into the war. Naruto, being the curious and adventurous ninja he is, might be the first to discover it. His friends and allies could be initially wary of this strange power, but as Naruto learns to control it, they see its potential in turning the tide of the war against powerful enemies such as Orochimaru or the Hidden Stone Village's forces.
One possible plot could be Naruto somehow obtaining the Gura Gura Fruit. He then has to learn to control its powers while still maintaining his own ninja skills. For example, he might accidentally cause earthquakes during battles at first, but as he masters it, he combines the fruit's power with his Rasengan, creating a super - powerful attack.
Naruto could use the Gura Gura Fruit to create huge tidal waves in battles near water sources. This would be a great advantage against enemies not used to fighting in water. For example, if facing the Sand Village ninjas, he could flood the desert battlefield, disrupting their attacks and movements.
Their relationship could become stronger. Kushina, with the Gura Gura no Mi, would be an even more powerful protector. Naruto would look up to her even more, and they would bond over the new power she has. He might ask her for training tips on how to use such a powerful ability.
One possible plot could be that Kushina somehow gains the powers of the Gura Gura no Mi. She could use it to protect Naruto from various threats in the Naruto universe. Maybe she could create powerful shockwaves to fend off enemies like the Akatsuki. Naruto, seeing his mother's new power, would be inspired to train harder and learn how to combine his own jutsu with the power of the Gura Gura no Mi.
He would likely be more isolated at first. The Magu Magu Fruit powers are different from normal ninjutsu. His friends might not understand it fully, and he would need time to master it alone. This would make him more introspective, but as he gets better control, he would start to share his knowledge and use it for the good of the village. Also, his fighting style would change drastically. Instead of relying solely on his shadow clones and Rasengan, he would incorporate the heat - based attacks of the Magu Magu Fruit, making him a more versatile fighter.
Naruto might become more cautious. Guns are very different from ninja tools, and one wrong move could be fatal. So he'd have to think twice before acting impulsively, which is a big change from his usual head - first approach.
Naruto would likely become more confident. With the powerful abilities of the Dragon Devil Fruit, he'd have an edge in combat. This new - found power could also make him more responsible as he'd have to control these dangerous abilities. For example, if he has the power to create powerful gusts of wind like a dragon's wings, he needs to be careful not to cause collateral damage.
If Sasuke had the Fire - Fire Fruit, his fire - based attacks would become much more powerful. His Amaterasu could potentially be even more destructive, as the Fire - Fire Fruit's flames might add an extra level of intensity. His fighting style would become more aggressive, relying on the overwhelming power of the fruit's fire to overpower his opponents.
If Naruto found a devil fruit, it would open up a whole new world of possibilities for his adventures. He could travel to different lands in search of more knowledge about the devil fruit. Maybe he'd encounter other characters from different fictional universes who are also interested in devil fruits. His understanding of power and the world around him would expand. He'd no longer be just a ninja from the Hidden Leaf, but someone with a power that bridges different fictional concepts. This could lead to him becoming a sort of ambassador between the Naruto world and the world of One Piece - like elements introduced by the devil fruit.