One idea could be a love triangle situation where the reader is a servant in a grand manor served by both Sebastian and Claude. The reader is initially charmed by Sebastian's suave and proper demeanor but then finds herself drawn to Claude's mysterious allure as well. They both compete for the reader's affection in a series of events that involve solving mysteries within the manor and protecting the master.
There's a fanfic called 'The Meeting of Shadows' which is quite interesting. In this story, Sebastian and Claude are forced to work together on a task by some mysterious force. It shows how they interact when they have a common goal, while still maintaining their enmity. It's a great read if you like exploring their dynamic.
One aspect to consider in this type of fanfiction is the complex relationships. Sebastian and Claude are both very distinct characters. Sebastian is often portrayed as sophisticated and devious in his own way. When a reader is inserted into the mix, it creates a love triangle -esque situation. The dynamic between them can lead to a lot of interesting plot developments. For example, the reader might be caught in the middle of their power struggles or their attempts to win the reader's affection could be full of intrigue and mystery.
A common theme is rivalry. Since they are often at odds in the original source material, this is carried over into many fanfictions. They compete for power, influence, or the attention of a certain character.
In uke claude faustus x sebastian fanfiction, the concept of 'uke' gives a particular slant to the relationship. It might imply a more submissive role for Claude in the story. This can lead to interesting plot developments where Sebastian takes on a more dominant position, perhaps in terms of decision - making or protecting Claude. The fanfiction could also delve into their backstories and how their past experiences shape their relationship in this new, fictional context.
A common theme is the love triangle. The OC is often in a difficult position of choosing between Sebastian and Claude. Another theme is power struggle. Since both Sebastian and Claude are powerful demons, their rivalry over the OC can also be seen as a struggle for power and influence.
One popular sebastian x oc x claude fanfiction is 'The Crossroads of Demonic Fates'. It has an interesting plot where the OC gets caught between Sebastian and Claude's power struggles. The character development of the OC is quite engaging as she tries to navigate the complex relationship between the two demons.
In Black Butler Claude x Sebastian fanfiction, a common theme is the exploration of their demonic natures. Writers often delve into how their demon instincts interact with their relationships. Also, themes of loyalty and betrayal are popular. For instance, what would make one of them betray their master for the other? It's all about the complex web of relationships and power dynamics that make these characters so interesting in fanfiction.
It is not appropriate at all. Fanfiction is a form of creative writing that should be based on respect for the source material and its audience. Sexual fanfiction, especially with yaoi themes in this case, can be seen as a form of exploitation. It may also be offensive to those who view the characters in a different light, and it does not contribute to the healthy development of the fan community.
A title like 'Claude Faustus and Sebastian Michaelis: A Forbidden Encounter in Fanfiction' would be interesting. It gives a sense of mystery and something that perhaps shouldn't be happening between them.