Luke Skywalker could be another key character. Since he is Vader's son, his presence could add an interesting dynamic. He might be the one who somehow triggers the battle between Anakin and Vader, or he could be in a position to influence the outcome of their fight, perhaps by appealing to the remaining good in Anakin or by facing off against Vader himself in a three - way struggle.
It really depends on how you write it. If it's Anakin at his peak before turning to the dark side, he has a lot of raw power and potential. But Vader has years of experience as a Sith Lord. So, it could go either way.
One idea could be a story that focuses on Anakin's internal struggle between his love for Padme and his fall to the dark side as Darth Vader, while Luke and Leia unknowingly grow up in the shadow of their father's actions. It could explore how their lives might have been different if Anakin had not turned, and how they eventually come to terms with his true identity.
In such a fanfiction, one possibility is that Anakin Skywalker might initially be in shock upon seeing Darth Vader. He could struggle to come to terms with what he has become. Maybe there would be a battle of wills as Anakin tries to fight against the dark side within Vader.
One way this could happen is through some sort of interdimensional rift. Maybe a powerful jutsu in the Naruto universe accidentally tears open a portal to the Star Wars galaxy. Naruto, being the curious and brave ninja he is, gets sucked into it. Once in the Star Wars universe, he's exposed to the dark side of the Force, which gradually corrupts him and he starts to take on the persona of Darth Vader. He might even learn some of the Sith ways from Vader's own teachings if he somehow travels back in time to Vader's era.
One possible plot could be that Naruto, through some strange magical or technological accident, gets transported to the Star Wars universe. There, he is influenced by the dark side of the Force and starts to take on the characteristics of Darth Vader. Maybe he has a run - in with Palpatine - like figure who manipulates him. He could start wearing Vader - like armor as a symbol of his new, darker self.
Anakin Skywalker's character development is a long and complex journey in 'The Rise of Darth Vader: A Star Wars Story'. In the beginning, he was a young, talented Jedi with a big heart. But his pride also grew as his power increased. He didn't like being told what to do by the Jedi Council. His relationship with Padmé was against the Jedi Code, which added to his internal conflict. As the story progresses, he faced more challenges and temptations. His desperation to save Padmé from a supposed death made him trust Palpatine more. Palpatine exploited Anakin's weaknesses, his love, his pride, and his doubts about the Jedi. This continuous manipulation and Anakin's own internal battles led to his downfall and the rise of Darth Vader.
A possible plot is a fanfic where Anakin, in his Darth Vader form, has a vision of a different future where he didn't lose Padme. This vision makes him question his loyalty to the dark side. Meanwhile, Luke and Leia are on a mission to rescue their father from the clutches of the Emperor. The story could be filled with emotional reunions and battles between the light and dark forces.
One common theme is redemption. Many fanfics explore the idea of Darth Vader still having a glimmer of Anakin inside and the possibility of his return to the light side. Another theme is the struggle with the dark side. Writers often depict Anakin's internal conflict as he fully embraces the power of Darth Vader. There's also the theme of lost love, especially his relationship with Padmé and how it affects him as Darth Vader.