Maybe Naruto starts to struggle with the dark side of the Rinnegan. Since the Rinnegan has some very powerful and potentially dangerous abilities, he could face internal battles. He might have to learn how to control the power without being consumed by it, like Sasuke had to with his Sharingan and later the Rinnegan. This could lead to a lot of self - discovery and growth for Naruto.
One possible plot development could be that Naruto gains a whole new level of power and is able to see and understand the world in a different way. He might be able to use the Rinnegan's abilities to finally bring true peace to the ninja world. For example, he could use the power of the Rinnegan to better understand the motives of his enemies and find non - violent solutions to conflicts.
Another plot development could be that Naruto's relationships with his friends and allies change. With the Rinnegan, he becomes an even greater force to be reckoned with. Some of his friends might be in awe of his new power, while others might be a bit scared or worried. This could cause some tension within the group, but also strengthen their bonds as they work through these new dynamics.
Another aspect could be the reaction of the other characters in the Naruto universe. Some might be fearful of the new power, thinking the character with the transplanted Rinnegan could become a threat. Others might see it as an opportunity to use this new - found power for their own purposes, like fighting against a common enemy. There could be a lot of political intrigue and power struggles within the ninja villages as a result.
A plot development might involve Naruto struggling to control the Rinnegan at first. Sasuke, noticing this, believes he can defeat Naruto easily with his Sharingan. But as Naruto starts to master the Rinnegan, he shows new abilities that shock Sasuke. This could lead to a situation where they have to team up against a common enemy who is after the power of both the Rinnegan and the Sharingan. Or perhaps a prophecy is revealed that states only one of them can keep their dojutsu power and they must fight to decide who keeps it, leading to a moral and power - based struggle.
One possibility is that Naruto's friends launch a rescue mission. They would use their unique skills, like Sasuke's Sharingan or Sakura's medical ninjutsu combined with her combat skills, to find and save Naruto.
In a fanfiction where Naruto is sealed away, there could be a focus on the emotional turmoil of his friends and family. Hinata, for example, might be extremely distraught and use her Byakugan in new ways to try and find Naruto. Sasuke could also return to the Leaf Village out of loyalty to Naruto and join the efforts to unseal him. The story could also explore how the younger generation of ninjas, inspired by Naruto's legacy, strive to become stronger to free him.
A plot could develop where Naruto and Tsunade try to keep the pregnancy a secret at first. As the pregnancy progresses, it becomes harder to hide. Naruto may start to train even harder to prove himself worthy of being a father and to protect his unborn child. Tsunade, on the other hand, might face challenges from the medical community as her pregnancy at her age could be considered high - risk. And there could be a rift in their relationship as they deal with the stress and the different ways they approach the situation.
In this 'naruto gets poisoned fanfiction', Naruto could also try to fight the poison using his own chakra. He might enter a state of inner struggle where he has to battle the effects of the poison on his body while still trying to protect the village. His Nine - Tails chakra could play a role, either helping him resist the poison or making the situation more complicated if it reacts badly with the poison.
One possible plot development could be that after saving Naruto, Madara tries to mentor him. He sees Naruto's potential and wants to shape him into an even greater ninja, sharing his own knowledge and skills that have been honed over years.
Another plot development could be that Naruto's Enton Release attracts the attention of an ancient and powerful organization. They see Naruto as a key to achieving their own goals, whether it's world domination or unlocking some sort of ancient power. Naruto has to fight against this organization while also trying to understand the full extent of his Enton Release and how it can be used to stop them.
One possible plot development is that Naruto gets to experience a different kind of family dynamic. Kurenai could introduce him to her friends in the village, expanding his social circle. This could help Naruto feel more integrated into the village community.
One possible plot development could be Naruto using his new jutsu to break Yugito free from an enemy's trap. Another could be that Naruto's words break Yugito's negative mindset.