One possible plotline could be that Naruto is cursed by a powerful dark jutsu during a battle. This jutsu slowly transforms him into a demon. As he changes, his friends initially try to find a way to reverse it. But Naruto starts to gain new powers that he must learn to control, and he has to struggle between his human side and the emerging demon nature.
One possible plotline could be Naruto being exposed to some sort of dark jutsu that warps his mind and makes him idolize Tobi. He might start to adopt Tobi's methods and goals, causing chaos in the ninja world. His friends would be shocked and try to bring him back to his senses.
One possible plotline could be that Naruto is exposed to a dark and powerful jutsu that gradually transforms him into a monster. He might start to lose his sense of self and his friends have to find a way to reverse the process. For example, Sasuke could use his Sharingan to try and understand the nature of the transformation and look for a weakness in the dark jutsu.
One possible plotline could be Naruto struggling to control his new demonic powers while still trying to protect the village. He might be feared by some villagers who sense his demonic nature, and he has to prove that he's still on their side.
One possible plotline could be that Naruto discovers a new jutsu that not only enhances his power but also changes his appearance. This jutsu might have some unforeseen side effects that gradually make him more and more handsome. For example, it could be related to chakra control and as he masters it better, his physical features start to change in a more appealing way. Maybe his hair becomes shinier, his eyes more piercing, and his face more chiseled.
Another plotline could involve Naruto being chosen by some ancient and powerful force to become a god. As a god, he has to deal with other divine beings. He may face challenges like jealousy from other gods or having to prove himself worthy in the divine realm while still caring about his friends and the village he left behind.
A plotline could be Naruto having to deal with the remnants of old enemies. Some of Orochimaru's followers might still be causing trouble, and as Hokage, Naruto has to stop them without using excessive force. He wants to show mercy but also protect the village. Another aspect could be Naruto working on the village's infrastructure. He realizes that a strong village isn't just about having powerful shinobi but also about having a stable and prosperous community. So he starts projects like building new schools for ninja training and improving housing for the villagers.
One possible plotline could be Naruto being shunned by the Hidden Leaf Village at first. Since demons are often feared in the Naruto world, his transformation into a full demon might make the villagers see him as a threat. He would then have to prove that he's still the same Naruto on the inside. Another plotline could involve him having to learn to control his new demon powers, which might be much more powerful and uncontrollable compared to when he had the Nine - Tails inside him.
A plot could involve Harry dealing with the Black family's old grudges and feuds. As Lord Black, he has to sort out the mess left behind by generations of Blacks. He might have to mediate between different branches of the family who have been at odds for centuries. Harry could use his own experiences of friendship and loyalty from his time at Hogwarts to try and heal the rifts within the Black family. This would not only change the Black family but also have a positive impact on the overall wizarding society as the Black family has a significant influence.
The plot could also involve a time - related crisis. Maybe something is threatening the timeline, and the only way to fix it is for future Naruto to raise his younger self in a certain way. So, future Naruto has to make sure that the younger Naruto grows up to be strong enough to face this threat while also maintaining the integrity of the timeline.
One possible plotline could be Yuu struggling with his new vampire nature while still trying to protect his friends. He might have to deal with the thirst for blood and resist the urge to harm his comrades. Another could be that he uses his new vampire abilities to fight against the real enemies of the series in a more powerful way. For example, he could use enhanced speed and strength to take on the vampires that are causing chaos in the world of Owari no Seraph.