A great idea for a fanfiction could be to set it in a parallel universe where Leo was always a Dark Signer. In this universe, he has different relationships with the other characters. For example, he could be a rival to Yusei from the start, and their duels could be epic battles for the fate of the city. His dark powers would be more developed, and he might have a different set of goals compared to his normal self in the original Yu - Gi - Oh 5D's story.
One idea is to have Leo's time as a Dark Signer be a sort of test. Maybe the gods or some higher power in the Yu - Gi - Oh universe are testing him to see if he can resist the allure of ultimate power. In this fanfiction, Leo would constantly be on the verge of succumbing completely to the dark, but there would be glimmers of his true self trying to break through. His duels could be a way for him to either gain more power or lose himself further, depending on how he uses his cards.
One possible fanfiction could be about Leo's transformation into a Dark Signer. It might explore his internal struggle between the dark power and his loyalty to his friends. Maybe he starts to have visions that the dark power shows him, of a world where he rules with great power, but at the cost of losing his true self.
There are many interesting fanfictions on this topic. Some might explore Carly's transformation into a Dark Signer and how it changes her relationships. For example, it could show her relationship with Jack becoming more complex as she is now on the 'dark side'.
A really interesting fanfiction I came across was about Yusei's encounters with other Dark Signers before fully becoming one himself. It showed how he was gradually influenced by the dark forces. In some fanfictions, the author might focus on Yusei's new deck as a Dark Signer. It could have cards with darker themes and more powerful but dangerous effects. These fanfictions can offer a different perspective on Yusei's character compared to the original series.
One possible plot could be Carly's initial confusion and fear when she first becomes a Dark Signer. She might not understand what's happening to her and tries to resist the dark power at first.
You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own (AO3). These platforms have a large collection of Yu - Gi - Oh fanfictions, and you can specifically search for ones related to Dark Signer Yusei.
One common theme is the internal struggle. Crow has to deal with the dark powers within him while still trying to hold on to his sense of self. Another is his relationships with the other characters. It might explore how they react to his transformation and how he interacts with them as a Dark Signer.
One popular one might be those that focus on their adventures in the Satellite. It could show Leo and Luna exploring new areas, facing challenges together, and growing as characters. Maybe they discover some new cards or duel strategies while in the Satellite.
A plot could involve a villain who is trying to combine the powers of the Shadow Clans in Naruto with the dark powers in Yu - Gi - Oh 5D's. Naruto and the Yu - Gi - Oh 5D's protagonists would then have to team up to stop this evil force. They would exchange their skills and knowledge, like Naruto teaching them some basic ninja techniques and the Yu - Gi - Oh 5D's characters showing Naruto how to use Duel Monsters effectively in combat.
You can start by looking on fanfiction websites such as FanFiction.net or Archive of Our Own (AO3). These platforms usually have a large collection of fan - created stories, including those related to Yu - Gi - Oh 5D's characters like Leo and Luna.
You can try looking on fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Crow Dark Signer Yu - Gi - Oh 5DS' and you might find some great stories.