In a 'yusei becomes dark signer fanfiction', perhaps Yusei discovers a hidden part of his past that links him to the Dark Signers. He could find out that his family was somehow involved with the dark forces in the past. This revelation shakes his sense of self. As a result, he decides to embrace the role of a Dark Signer to fully understand his heritage. However, he soon realizes that the power comes with a price, and he has to fight against the corrupting influence of the dark energy while still trying to achieve his own goals.
Some common themes in Dark Signer Yusei fanfiction could be redemption. Since the Dark Signers are often seen as antagonists, fanfics might explore their journey towards redemption. Another theme could be power struggles. Yusei, being a powerful duelist, might face intense power battles against the Dark Signers in these stories. Also, friendship can be a theme as Yusei tries to understand the Dark Signers and maybe even form an unlikely bond with them.
Crow Hogan is often a popular character to include. He's Yusei's friend and his presence can add more depth to the story. Another one could be Jack Atlas. His rivalry with Yusei and his strong personality make him a great addition. Also, Akiza Izinski might be included as she has her own powers and a connection to Yusei.
Romantic relationships would also be affected. If Yusei had a love interest, she or he would be heartbroken and confused. They might try to reach out to Yusei and bring him back from the dark side. But Yusei, as a Dark Signer, might push them away, believing that his new path is one he has to walk alone. His relationships with his mentors or older figures in his life would also turn sour, as they would see him as having strayed from the right path.
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.
Perhaps a fanfiction where Akiza is transported to an alternate dimension as a Dark Signer. In this new world, she has to use her powers to survive and find a way back home. Along the way, she forms new relationships and has to face off against powerful enemies who are intrigued by her Dark Signer abilities.
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 plot idea could be Carly's journey as a Dark Signer. Maybe she discovers a hidden power within her Dark Signer status and has to decide whether to use it for good or be consumed by the darkness. For example, she could use it to protect her friends from other more malevolent forces in the Yu - Gi - Oh universe.
One interesting concept could be the origin of the Dark Signers. Maybe they were once normal duelists who were corrupted by a powerful and ancient force. Another could be their unique connection to the spirit world, like how they can summon darker versions of monsters. And also, the idea of their ultimate goals, whether it's about ruling the dueling world or something more sinister related to the secrets of the cards.
A prevalent theme in 'yugioh dark signer fanfiction' is the battle between good and evil. Even though the Dark Signers are on the 'dark' side, some stories show them having a chance at redemption, blurring the lines between good and evil. There are also themes related to sacrifice. Some Dark Signers might have to sacrifice their powers or relationships in order to achieve a certain goal, like saving someone or changing their own destinies.
First, you need to know the basic lore of the Dark Signers in the Yu - Gi - Oh! series. Then, think about a unique plot. It could be centered around a new Dark Signer character you create or an existing one with a different backstory. Next, decide on the setting. Is it in the original Yu - Gi - Oh! world or a modified version? After that, start with an interesting opening, like a mysterious event related to the Dark Signers.