In this fanfiction, Naruto could control all the tailed beasts because of his unique chakra nature. His chakra is very special and has a high compatibility with the tailed beasts' chakra. Also, his experiences with Kurama might have given him insights on how to handle other tailed beasts. He probably communicates with them on a spiritual level and convinces them to work together with him.
Well, in many fanfictions, Naruto might use his strong will and the power of his Uzumaki heritage. His natural chakra reserves are huge, which helps. He also has a deep understanding of friendship and the tailed beasts' pain from his own experiences. So, he can connect with them on an emotional level and gradually gain their trust, thus being able to control them.
One interesting storyline could be about the tailed beasts forming an alliance outside of the control of humans. They might work together to protect their own kind and the world in a different way than the shinobi. For example, they could create their own hidden land where all chakra - based creatures are welcome.
In this fanfiction, Naruto would gain the ability to manipulate the elements in new ways. Each tailed beast is associated with a different element or combination of elements. By having all of them, he could create complex elemental attacks that are not possible before. For instance, he could combine the fire of one tailed beast with the water of another to create steam - based attacks. His healing factor might also be enhanced as some tailed beasts possess regenerative abilities. This would make him even more difficult to defeat in combat.
In such fanfiction, Naruto may gain the ability to heal himself more quickly. Since the tailed beasts possess a great amount of life - force energy, Naruto could tap into that to accelerate his own healing process. His mental abilities could also be enhanced. He would be able to withstand greater mental pressure and use the tailed beasts' collective wisdom to make better decisions in battles. Moreover, he could potentially create a chakra shield that is extremely strong, using the combined chakra of all the tailed beasts to protect himself and his allies.
Well, it would drastically change the power balance. Naruto already had a strong connection with the Nine - Tails. Having 3 tailed beasts would make him an even more formidable force. His enemies would be much more cautious around him. He might also have to deal with the different personalities and powers of each tailed beast, which could be a challenge to control all at once.
If Naruto gets all the tailed beasts in the fanfiction, it would change the power dynamics completely. He could use their unique abilities in combination. For example, the Shukaku's sand control along with the Nine - Tails' chakra. This would make him a force to be reckoned with not only in combat but also in terms of politics and diplomacy in the ninja world. Other villages might see him as a threat or as a new leader to follow. And his relationships with his friends and allies would also evolve, as they would have to adjust to this new, super - powerful Naruto.
It would change a lot. Firstly, the village's perception of Naruto would be different. They might see him as an even greater asset or a greater threat, depending on how they view the tailed beasts. Also, his training would be different. He'd have to learn to control two powerful entities inside him, which could be a whole new level of difficulty compared to just one. And in battles, he could potentially use the two tailed beasts to double - team opponents or combine their abilities for a super - powerful attack.
Kurama is often a very popular character. As the Nine - Tails, he has a long history with the main Naruto storyline and his complex relationship with Naruto makes him interesting in fanfiction. He has a lot of power and a fiery personality.
The abilities would be numerous. Naruto could gain the power of enhanced perception from one of the tailed beasts, being able to sense enemies from much greater distances. Another tailed beast might give him the ability to manipulate earth, allowing him to create earthquakes or form defensive earth structures. And with the combined power of three tailed beasts, he could potentially break through any type of chakra - based defense. His stamina would also be greatly increased, enabling him to fight for longer periods without getting tired.