Sure, there are. In some fanfictions, the dynamic between Sakamaki Yui and her vampire sister is really captivating. They might have different personalities, with Yui being more innocent perhaps and her sister having a more complex and mysterious side. These differences can lead to interesting storylines, like when they face a common enemy or when they have a disagreement about the vampire lifestyle and how they eventually resolve it.
One common theme is the exploration of family relationships within the vampire context. Since they are sisters in a vampire family, there could be themes of loyalty and betrayal. Another theme could be the struggle for power or acceptance among the vampires.
In 'shu sakamaki x yui fanfiction', the character development is an interesting point. Shu may evolve in his feelings towards Yui, perhaps starting from indifference or mild annoyance and gradually growing into something deeper like love or a strong protectiveness. Yui, on the other hand, could become more assertive or more resigned in her relationship with Shu as the story progresses.
Love is a very common theme. Given the nature of the two characters, it could be a complex, often angsty love. There might be a struggle between their different personalities and the situations they are in.
Love and redemption are common themes. Subaru often has a troubled past, and through his relationship with Yui, he finds a sense of redemption. Yui's love helps him heal. For example, in many stories, Subaru's initial coldness melts away because of Yui's unconditional love.
One popular subaru sakamaki x yui fanfiction is 'A Chance Encounter'. It beautifully portrays their relationship with Subaru's brooding nature and Yui's gentle kindness interacting in an interesting way. The story has a lot of emotional depth and the author does a great job of building up the tension between the two characters.
Besides Yui, there could be a group of young vampires who take Yui under their wing. They could be fun - loving and introduce Yui to the vampire nightlife. Then there might be an older vampire mentor figure who tries to guide Yui in controlling her powers. And a human love interest from Yui's past who still has feelings for her and tries to bring her back to the human side.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfics, and you can easily search for 'yui x sakamaki brothers fanfic' in its search bar. There are likely to be many different stories there, with various interpretations of the relationship.
One popular 'yui x sakamaki brothers fanfic' might be those that focus on Yui's initial encounters with each of the Sakamaki brothers. For example, a story could be about how Yui first meets Ayato and the immediate tension and attraction between them. Another could explore the more complex relationship she has with Subaru, delving into his brooding nature and how Yui tries to reach out to him.
One possible plot could be that Yui, an ordinary girl, gets bitten by a vampire. She then has to deal with her newfound vampiric instincts like a craving for blood. She might struggle to fit into the vampire society which has its own rules and hierarchies. Maybe she tries to resist her darker urges and find a way to co - exist with humans.