Well, it could be about Naruto having to deal with the power of two Bijuus. Maybe he struggles to control their combined power at first. He might face new and more powerful enemies who are after the power he now holds. And there could be a whole new arc of training to master this unique situation.
In this fanfiction, it could be that Naruto, as the Jinchuriki of two Bijuus, discovers new jutsus or abilities that come from the combination of the two. He may have to go on a journey to understand the origin of these two Bijuus and how they came to be in him. This could lead to uncovering ancient secrets about the ninja world and his own family history. His friends might also have different reactions, some being in awe of his new power, while others might be worried about the changes in him.
It could be Orochimaru. He's always been after power and Naruto having the power of two Bijuus would be very tempting for him. He might try to extract the Bijuus from Naruto to use for his own evil purposes.
Well, it could change the plot in many ways. For one, Naruto would be incredibly powerful right from the start. His relationships with other characters might also be different. Since he's the Jinchuriki of multiple Bijuus, the village's view of him could be more of a weapon than a person. And he might have to deal with more internal struggles as he tries to control all that power.
In this fanfiction concept, Naruto's new abilities could be vast. He might be able to access a new form that combines the features of all the Bijuus he houses. This form could have multiple tails, each representing a different Bijuu, and with each tail comes a different power. For instance, one tail could give him the ability to control water like the Three - Tails, while another could grant him the power of fire like some of the other Bijuus. He could also develop the ability to share the power of the Bijuus with his allies in a limited way, making his team even more formidable in battle.
Well, perhaps the fem Bijuus see Naruto as a symbol of hope even as a baby. They could start influencing his dreams, giving him visions of a united ninja world. In the fanfiction, this might lead to Naruto having an early understanding of the importance of peace. He could then start showing extraordinary wisdom for his age, which would puzzle the villagers. And as he grows, his actions would be more guided by these early dreams influenced by the fem Bijuus.
Well, it could be about Naruto somehow obtaining the power of Son Goku. Maybe there's a strange jutsu that fuses their powers. Naruto could use Son Goku's strength in battles, like having his speed and ki blasts along with his own ninja skills.
Well, the plot could involve Itachi having to deal with the power of the tailed beast within him. Maybe he has to constantly struggle to control it while still maintaining his calm and collected exterior. He could use the power in unexpected ways to protect his village or those he cares about, like Naruto does with the Nine - Tails.
It could also be a form of building alliances. By reaching out to the Jinchuriki through letters, Naruto is establishing a connection. This can be important in the Naruto universe where having allies is crucial for the safety of the villages and the world at large. He may be hoping to create a united front among the Jinchuriki against common enemies.
The fem Bijuus might interact with Naruto in a very nurturing way. For instance, they could use their chakra to soothe him when he is crying. They may also communicate with him on a spiritual level, sharing their stories and wisdom. Maybe the Bijuus would play games with Naruto, like simple chakra - based games to help him develop his skills early.
A possible plot twist in this fanfiction might be that Naruto's new status as the jinchuriki of Saiken attracts a new group of enemies who are specifically after the power of the Six - Tails. Also, there could be a situation where Naruto's friends start to fear him because of Saiken's power, thinking he might lose control. And perhaps there is a hidden prophecy that only Naruto as the jinchuriki of Saiken can fulfill, which leads to a whole new adventure and set of challenges for him.
In this kind of fanfiction, Naruto might grow up with a better understanding of his Jinchuriki status from the start. He could be trained in a more specialized way. For example, he might learn unique jutsu related to the Nine - Tails' power earlier. Also, he could have more comrades who are also Jinchurikis, and they could form a strong bond, sharing their experiences and difficulties. This could lead to a Naruto who is more confident and in control of his power compared to the original story.