Through intense battles on the battleship. In the heat of combat, Naruto might discover that he can use his Nine - Tails chakra in a new way to boost the power of the battleship's engines or shields, which is a new ability born out of necessity.
The concept of Naruto being the Ashura reincarnation can be used to develop new characters in multiple ways. One could be creating a group of anti - reincarnation fanatics. They believe that the cycle of reincarnation is disrupting the natural order and target Naruto. Each member of this group could have different motives and backstories. Also, there could be a character who is a self - proclaimed 'prophet' of the Ashura reincarnation. They claim to have insights into Naruto's future based on ancient texts related to Ashura, but their true intentions are not so clear at first. They could either be a help or a hindrance to Naruto as he discovers more about his reincarnation.
He could develop some sort of psychic power that doesn't rely on chakra. This could be a power related to his willpower, allowing him to influence the minds of his opponents or sense their intentions from a distance.
Another ability Naruto could develop is enhanced stealth. Itachi is known for his stealth and ability to move undetected. During the three - year training, Itachi could teach Naruto how to move more quietly, hide his chakra signature better, and approach opponents without being noticed. This would give Naruto an edge in combat, especially when facing more powerful opponents where a surprise attack could be crucial.
In this fanfiction, Naruto could potentially develop the ability to create dark energy constructs like Raven does. For example, he could form weapons out of this energy, giving him an extra edge in close - combat situations. He may also inherit Raven's power of flight, which would completely change his mobility in battles and how he approaches combat scenarios. Additionally, Naruto could gain the power to absorb and redistribute energy, which could be used to either heal himself or boost his attacks. This new set of abilities would not only make Naruto more powerful but also open up new storylines and character developments within the fanfiction.
If you become an animal in this fanfiction, your character could develop new abilities through training. For example, if you're a wolf, you could train to run faster and have better endurance in the wild. You might also learn how to communicate with other animals in the forest, which could be a useful ability for gathering information.
He could develop the ability to combine the power of the Sharingan with the Nine - Tails' chakra. Maybe he could use the Sharingan to better control the Nine - Tails' power, for instance, seeing the flow of the chakra inside him more clearly. This could lead to new jutsu that are a fusion of Uchiha and Uzumaki techniques.
He could develop the ability to better withstand the different climates in One Piece. Since he's immortal, he might experiment with his body in ways others can't. Maybe he could learn to breathe underwater like a fish - man over time due to his long - lasting life.
He could develop the ability to use the Six Paths Sage Mode more effectively. Since the Rinnegan is related to the Sage of Six Paths, it would enhance his connection to that power. He might also gain the ability to create chakra chains similar to those of the Uzumaki clan but with an added Rinnegan - powered twist.
His physical abilities would likely improve a great deal. Black Widow is a master of martial arts, so Naruto could become even more formidable in close - quarter combat. His agility and strength could be enhanced beyond what he achieved in the ninja world just through her training methods.
Naruto would likely develop his chakra control better. The toads could teach him unique ways to manage his chakra, like using it in harmony with the natural energy around him. This would make his Rasengan and other jutsu more powerful.