One interesting plot could be a character in the fanfiction having a heart of stone due to a past trauma, like losing their family in a ninja war. And Naruto, with his usual determination, tries to break through that cold exterior. For example, he might start by befriending the character during a joint mission and slowly uncover the reasons behind their cold - heartedness.
Perhaps in this fanfiction, there's a new villain with a heart of stone who is immune to normal jutsu because of their emotional detachment. Naruto then has to find a way to reach their humanity. He could try using his own experiences of being an outcast in the village to relate to the villain. This creates a unique dynamic where Naruto's empathy is pitted against the villain's cold - hearted resolve.
In 'Hearts of Stone Naruto Fanfiction', there might be a plot where Naruto discovers a hidden clan whose members are all born with hearts of stone metaphorically. They have different abilities because of this. Naruto has to learn about their culture and way of life in order to gain their trust and assistance in a greater battle against a common enemy. This would involve him facing challenges in understanding their cold and logical approach to life compared to the more emotional shinobi world he is used to.
Well, Naruto is most likely one of the main characters. Given it's a Naruto fanfiction, he would probably be central to the story, whether it's him trying to change someone with a heart of stone or dealing with his own challenges related to that concept. Another character could be a new OC (original character) created specifically for this fanfiction. This OC might be the one with the heart of stone that Naruto has to interact with.
One interesting plot could be that the ponies from MLP accidentally find themselves in the Kingdom Hearts universe. They might mistake the Heartless for some kind of dark magic creatures from their own world and try to fight them using their magic. For example, Twilight Sparkle could use her powerful spells to combat the Heartless while trying to figure out how to get back to Equestria.
Some crossovers might involve the villains. Orochimaru could be interested in the power of the Heartless or the Keyblades. He might try to manipulate the situation in the Kingdom Hearts world. And the Organization XIII members could see Naruto's unique powers as a threat or a tool for their own plans. This would lead to some intense battles and strategic alliances between the characters of both series.
One concept could be Naruto and his friends being Keyblade wielders. They could travel between different worlds in the Kingdom Hearts style, using their ninja abilities along with the power of the Keyblade. For instance, Naruto's Rasengan could be combined with a Keyblade attack. Another idea is that the Akatsuki are like the Organization XIII in Kingdom Hearts, with each member having their own unique powers and goals related to both the Naruto world and the Kingdom Hearts concepts of hearts and darkness.
Well, in a 'Naruto Power Stone fanfiction', perhaps the power stone is from another dimension. Naruto finds it during one of his missions. This stone could grant him the power to communicate with all living beings telepathically. He could then use this power to bring peace between the different ninja villages by understanding their true needs and desires.
One interesting plot could be Naruto coming back with new and enhanced powers. Maybe he has a special connection to a new chakra source that was unknown before his revival. This would make him even more powerful and able to face new threats that emerged during his absence.
One interesting plot could be that Naruto, through some sort of magic or strange portal, ends up in the world of Candace. He could use his ninja skills to help Candace deal with the pesky brothers who are always causing trouble. Maybe he teaches her some basic ninja moves like how to do a simple substitution jutsu to outwit her brothers when they are planning their next prank.
Well, in some 'naruto is hokage fanfiction', there might be a plot where Naruto discovers a long - lost secret about the Hokage position. Maybe it's a hidden power that only the true Hokage can unlock. And then there could be a story line where Naruto has to balance his family life with his duties as Hokage. His kids might get involved in some dangerous situations that he has to handle while still leading the village.
One interesting plot could be Naruto coming back reanimated and having to team up with his former enemies who are also reanimated to fight a new, greater threat. This would turn the whole idea of enmity on its head.
One interesting plot could be Naruto as a girl facing unique challenges in the ninja world. For example, she might have to deal with different expectations regarding her appearance and gender role while still striving to be a great ninja. Maybe she uses her femininity in unexpected ways to outwit her opponents, like using charm as a distraction during a battle.