The 'slow - burn romance' is quite prevalent. Writers like to build the relationship between Sebastian and the female oc gradually, showing their growing attraction and connection over time. There's also the 'mysterious origin' trope for the female oc. She might have a hidden past or special powers that draw Sebastian to her, and this mystery unfolds throughout the story, adding depth and intrigue to the relationship.
A common trope is the 'forbidden love' trope. Since Sebastian has his own duties and often a dark nature in many interpretations, a relationship with a female oc can be seen as something that goes against the norm or is dangerous. Another is the 'damsel in distress' trope where the female oc gets into trouble and Sebastian has to save her.
One common trope is the 'fish out of water' situation. For example, if the OC is from a different time or place than the canon world, like an OC from modern times ending up in Middle - earth in a Lord of the Rings 'oc x cannon fanfiction'. Another is the 'love at first sight' trope, where the OC and the canon character fall for each other immediately. It's often used to quickly establish a relationship in the story.
One often - seen trope is the 'oc with a special power'. This power can either be a threat or an asset to the Akatsuki. It creates interesting dynamics as the Akatsuki members might want to use the oc for their power or protect them from others who would. Also, there's the 'redemption arc' trope for the Akatsuki through the oc's influence. The oc might make one or more of the members question their actions and seek a different path.
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 common trope is the over - protective yandere. The yandere character in these fanfics often goes to extreme lengths to protect the Marvel OC, even if it means going against other characters or the law. For example, they might fight off villains in a very brutal way just to keep the OC safe.
One common trope is the 'opposites attract' scenario. The grand highblood's often menacing or complex nature is contrasted with the oc's more innocent or different qualities. This creates a dynamic relationship.
One common trope is the 'outsider who understands'. The OC is often an outsider in some way, whether it be from a different village or having a unique power, but they seem to understand Sasuke on a deeper level than others. Another is the 'love - against - all - odds' trope. Since Sasuke is a complex and often aloof character, the OC usually has to overcome many obstacles to get close to him.
One popular trope is the 'Forbidden Love' aspect. Since Sebastian is a demon and Ciel is a human, their relationship can be seen as something that goes against the natural order. Another is the 'Power Struggle' trope. Ciel may try to assert his authority over Sebastian, but Sebastian's demonic nature gives him an edge in certain situations. 'Soul Bond' is also common. Given their contract and the connection it implies, fanfictions often explore the deeper spiritual and emotional bond that might develop between them.
Well, one common trope might be the 'damsel in distress' where the abused oc is constantly in need of rescue. Another could be the alpha's over - the - top possessiveness being seen as a form of 'love' even though it's not healthy. But again, this is a rather dark and not - so - positive set of tropes.
One common theme is the power dynamic. Since Sebastian is often a powerful character, the relationship with the OC can explore how power is balanced or unbalanced between them. For example, in some stories, the OC might be initially powerless against Sebastian but then find ways to assert themselves.
One common theme is the exploration of a romantic relationship between Sebastian and the OC. Writers often create scenarios where the two characters are drawn to each other in unexpected ways.