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 also try searching on social media platforms. There are groups or pages dedicated to Yu - Gi - Oh fanfiction. Sometimes fans will post their stories directly there or share links to where they can be found. Just be sure to check the rules of the group or page before posting any requests.
Another place could be some Yu - Gi - Oh dedicated forums. There are often sections where fans share their own fanfictions. However, the quantity might be more limited compared to the large - scale fanfiction platforms. But it's still worth checking out as you might find some unique and well - written stories about Leo and Luna there.
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.
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.
Some Tumblr blogs are also a great source for fanfiction. There are many fans who share their works or reblog interesting fanfictions. You can search for tags related to Naruto, Yu - Gi - Oh, and Luna. But be aware that Tumblr's search function can be a bit tricky sometimes, so you might need to be patient and try different combinations of keywords.
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 plot could be that Naruto, somehow transported to the Yu - Gi - Oh! 5D's universe, meets Luna. Maybe Naruto's ninja skills could be incorporated into the Duel Monsters world. For example, he could use his speed and stealth to help Luna in a dangerous situation, like when she's being threatened by some shadowy organization in the Yu - Gi - Oh! world that wants to steal her powerful cards.
Luna's ability to communicate with Duel Monsters could be combined with Naruto's chakra control. Naruto could transfer his chakra to the monsters Luna communicates with, making them stronger. This way, they could have an edge in battles. Also, Naruto's summoning jutsu could be used to call forth powerful creatures that could work in tandem with Luna's Duel Monsters in a unique combat scenario.
There are also some dedicated anime fanfiction forums where users share their works. However, the quality and availability may vary. You might need to do a bit of searching and browsing through different sections to find the specific harem fanfictions for these shows.
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.
Some popular fanfictions might involve epic adventures where the characters from both series team up. Maybe Naruto and his friends meet Yugi and his gang, and together they face a common enemy. Luna could be the key to unlocking a new power or a hidden mystery. These types of stories often draw in readers who love to see different fictional universes collide and interact in unexpected ways.
You can try websites like Fanfiction.net. It has a large collection of Yu - Gi - Oh fanfictions, and you might be able to find some specifically about Noah's love stories by using the search function. Just type in relevant keywords like 'Yu - Gi - Oh Noah love' and browse through the results.