A third common theme is the idea of redemption or change. Sephiroth is a complex character, often seen as a villain. In a crossover, he might be influenced by the Sekirei world and its characters to change his ways. Or, the Sekirei characters might be forced to confront a more malevolent force in the form of Sephiroth, and they have to adapt and find a way to either defeat or redeem him.
Another theme could be the cultural differences between the two universes. The Final Fantasy world has its own set of values, and the Sekirei world has its own. Fanfiction might play with how characters from these different cultures interact and adapt. For example, Sephiroth might find the concept of Sekirei pairs very strange at first. It can lead to interesting character development and relationship building within the story. And this often makes for an engaging read as the author tries to blend these two very different worlds together in a believable way.
One common theme is the clash of two different worlds. Shirou comes from the Fate universe with its own set of rules, magic, and values, while the Sekirei world has its unique system of Sekirei, Ashikabi, and battles. Another theme is adaptation. Shirou has to adapt to the new rules and environment of the Sekirei world. For example, understanding how to form bonds with Sekirei as an Ashikabi.
A common theme is power combination. Writers often explore how Naruto's powers, like his Rasengan or Shadow Clone Jutsu, can be combined with the Sekirei's powers. Another theme is the clash of cultures, as the ninja world of Naruto and the modern - yet unique - world of Sekirei collide.
Power - up is a common theme. Since Naruto is godlike, it usually involves him having super - enhanced powers in the Sekirei world. Another theme could be relationship building, like how he interacts with the Sekirei characters.
Well, one place to look for such fanfiction is on Archive of Our Own (AO3). They have a wide variety of fan - created works. Just search for 'sephiroth sekirei crossover' on their site, and you might find some interesting reads.
One common theme is her relationship with other Sekirei. Since she is a significant character in the Sekirei world, many fanfictions explore how she interacts with her peers, whether it's in a friendly or competitive way.
One common theme could be power. Both Harry and Sephiroth are associated with great power in their respective universes. So, fanfictions might explore how Harry's new - found connection to Sephiroth affects his power levels or how he uses it. Another theme could be identity. Harry having elements of Sephiroth in him might make him question who he really is.
Isolation is also quite prevalent. Vampires are often solitary creatures, and Sephiroth, being as complex as he is, is shown to be isolated even more so in these fanfictions. He may be shunned by others due to his vampiric state, or he may choose to isolate himself because of his new - found powers and the thirst that comes with being a vampire. And there's also the theme of the unknown. His vampiric abilities and how they work are often a mystery, and the fanfictions usually unfold this mystery gradually.
One common theme is redemption. Many fanfictions try to explore the possibility of Sephiroth finding redemption through his interactions with the original character. For example, the OC might show him a different way of life or values.
In many Sekirei OC Ashikabi fanfictions, the theme of self - discovery for the OC Ashikabi is present. They are often thrust into this strange world of the Sekirei Plan and have to figure out who they are and what they are capable of. Additionally, the exploration of the Sekirei's own personalities and pasts in relation to the OC Ashikabi is also a common theme. This can add depth to the relationships and the overall story.
A common theme is power. Since both Dragon Ball and Sekirei have characters with various levels of power, fanfictions often explore how these powers interact or compare. For example, how a Sekirei's special abilities would fare against a Super Saiyan's power.