Well, having gills would obviously make him better at underwater activities. He could swim faster and stay underwater for longer periods, which could be useful in battles near water or in underwater missions.
Maybe it's a strange genetic experiment gone wrong. Some evil scientist in the fanfic world might have tampered with Naruto's DNA, adding some sort of aquatic - like genes that resulted in gills.
The addition of Hashirama's chakra to Naruto in the fanfiction would be a game - changer for his abilities. Firstly, his stamina would likely skyrocket. Hashirama was able to fight for long periods without tiring, and Naruto could inherit this. Secondly, his sensory abilities might improve. Hashirama had a good sense of his surroundings, and Naruto could use this to detect enemies from a greater distance. Thirdly, his rasengan and other chakra - based attacks could be infused with the unique properties of Hashirama's chakra, making them more powerful and perhaps having additional effects like being able to break through stronger defenses more easily.
If Naruto had Konan's bloodline in the fanfiction, his abilities would change quite a bit. Konan can manipulate paper at will. So Naruto could use this to his advantage in combat. He could make paper shurikens that are as sharp as normal ones but more difficult to detect due to their lightness. Moreover, he could potentially use the paper to infiltrate places. He could send out a flurry of paper sheets and use them to spy on enemies or gather information from a distance.
If Naruto has Obito's eyes in fanfiction, his abilities would be enhanced in several ways. The Sharingan's ability to see chakra flow clearly would allow Naruto to better analyze his opponents' moves and weaknesses. With Kamui, he could teleport himself or objects, which would be a huge advantage in battles. He might also be able to use some of the more advanced Sharingan - related genjutsu, adding another layer to his combat skills.
In a fanfic scenario where Naruto has Madara's eyes, it would be a game - changer for his abilities. First off, the basic Sharingan abilities would boost his combat awareness. He'd be able to react faster and with more accuracy. The more advanced forms of the Sharingan, like the Eternal Mangekyo Sharingan if he were to achieve it, could grant him access to powerful techniques. For example, he might be able to use space - time ninjutsu similar to Madara. This would not only change the way he fights but also how he strategizes in battles, as he would have a whole new set of tools at his disposal.
Well, if Naruto had Kakuzu's abilities, he'd be a much more formidable fighter. Kakuzu could use multiple hearts to gain different elemental powers. Naruto could use this to his advantage in battles. For example, in fights against strong opponents like Pain, he could use the extra elemental powers to counter Pain's various abilities more effectively. It would also change his relationships. His friends might be a bit wary of him having such strange and powerful new abilities.
His chakra control might be affected by the different magical energies in the DxD world. Maybe his chakra could interact with the devil or angelic powers in unexpected ways. For example, his Rasengan could gain new properties if combined with devilish power. His shadow clones might also be able to do things like sense magical auras, which they couldn't do in the Naruto world.
Well, it could potentially enhance his physical capabilities like strength, speed, and endurance. Maybe he could gain new jutsu related to the bloodline. For example, if it was a fire - based bloodline, he might be able to create more powerful and unique fire - based attacks that he couldn't do before.
Well, having Shisui's eyes would likely give Naruto enhanced genjutsu abilities. Shisui's eyes are known for their powerful genjutsu. Naruto could use this to deceive his opponents more effectively in battle. He might be able to cast illusions that are much more difficult to break, and it could also potentially give him an edge in stealth operations as he could use the genjutsu to misdirect enemies.
Well, if Naruto has Shisui's eyes, he would likely gain the power of the Sharingan. The Sharingan can copy jutsus just by seeing them once. So Naruto could potentially learn a whole lot more jutsus much faster. And with Mikoto involved in the fanfiction, perhaps there's some connection to the Uchiha clan that gives Naruto a deeper understanding of their ways and powers. This could make him even more formidable in battles, as he combines his own Uzumaki chakra and tenacity with the powers associated with the Uchiha.