A great idea for a Naruto dark style fanfiction is to explore the psychological toll of being a ninja. For instance, what if ninjas who have committed heinous acts during missions start to lose their sanity? You could create a story around a group of such ninjas who band together, not for any noble cause, but because they feel they are outcasts in the normal ninja society. They might start causing havoc in the hidden villages, and it would be up to some of the main characters to stop them while also dealing with their own internal demons.
One idea could be exploring the dark side of the ninja world's politics. For example, showing how the hidden villages might secretly manipulate events for their own gain, even if it means sacrificing some of their own ninjas. Another could be delving into a darker version of Naruto's character, perhaps if he was corrupted by the power of the Nine - Tails in a more extreme way. Maybe he becomes more ruthless in his pursuit of power to protect the village.
In 'dark angel naruto fanfiction', a common idea could be a new type of jutsu inspired by the technology in 'Dark Angel'. For example, a jutsu that mimics the superhuman speed or strength of the 'Dark Angel' characters. Also, the concept of a hidden organization in Naruto that has similar goals or methods as the ones in 'Dark Angel' could be really interesting, like an organization that experiments on shinobi in a way that blurs the line between good and evil.
One interesting idea could be a unique take on Naruto's power. Maybe in this fanfiction, Naruto discovers a new form of chakra that's related to his 'dark genius' side. For example, it could be a chakra that allows him to manipulate shadows in a way no one else can.
Perhaps they are living in a parallel universe where everything is dark and gloomy. Dark Naruto and Dark Kushina could be trying to find a way to break through to the normal universe. They might encounter strange versions of their friends and foes, and have to battle their own inner demons along the way. For example, Dark Naruto might struggle with the darker aspects of the Nine - Tails' power that he has fully embraced in this universe.
One plot idea could be that Dark Naruto forms an alliance with Dark Kyuubi to take over the Hidden Leaf Village. They use their combined dark powers to manipulate the villagers and turn them against each other. Another idea is that they embark on a journey to find a powerful, ancient artifact that can enhance their dark abilities even further. Maybe they face off against the original Naruto and Kyuubi in a final battle of good versus evil.
One plot idea could be a story where in a dark alternate universe, Hinata is forced to become a spy against Naruto. She struggles with her loyalty to her village and her feelings for Naruto. Another could be that a dark force corrupts Hinata's mind, making her see Naruto as an enemy, and Naruto has to find a way to break the spell.
One idea could be a Naruto - style character being trained in the ways of the Dark Jedi. Maybe Naruto discovers an ancient Sith artifact in the Naruto world that gives him access to Dark Side powers, like enhanced chakra manipulation with a dark twist.
One idea could be that Dark Naruto has to face his inner demons while Naruko tries to save him. Maybe there's a villain who is trying to manipulate Dark Naruto's power for evil purposes and Naruko discovers this and has to fight both the villain and convince Dark Naruto to resist the dark influence.
One idea could be exploring Dark Naruto's internal struggle. Maybe he's constantly fighting against the dark chakra within him and how that affects his relationships with the other characters in the Naruto universe. He could be on a journey to find a way to control or purge the darkness without losing his identity.
One idea could be Dark Naruto forming an uneasy alliance with the Kyuubi. They might decide to take on the Hidden Leaf Village together, believing it has wronged Naruto in some way. Naruto could use the Kyuubi's power in a more sinister way than ever before.
One plot idea could be that Dark Naruto, who has been influenced by some dark force, sees Ino as a key to unlocking a hidden power within himself. Ino, on the other hand, tries to use her mind - related jutsu to understand what's wrong with Naruto and ends up getting caught in his dark world. She has to fight against his darker impulses while also trying to save him from whatever is corrupting him.