One popular theme is their relationship development. Fans often explore how their bond grows over time, from being comrades to something more. Another theme is adventure. Writers might create scenarios where Yuu and Shinoa go on special missions together, facing various challenges and enemies.
In fanfiction, Yuu's character might be developed by showing his vulnerability more when it comes to Shinoa. For example, he could be more open about his fears and insecurities around her. Shinoa, on the other hand, could be developed by showing her softer side towards Yuu. She might let down her tough - girl facade and be more affectionate.
You can try fanfiction websites like Archive of Our Own (AO3). There are usually a lot of works related to Yuu and Shinoa from Owari no Seraph there. Just search for their names on the site.
One interesting plot could be Yuu and Shinoa getting separated during a dangerous mission against the vampires. Yuu goes on a solo journey to find Shinoa, facing many challenges along the way. He has to battle powerful vampires and also deal with his own inner demons. When he finally finds Shinoa, they realize their bond has grown even stronger.
A popular fanfic in this pairing is 'Shinoa's Perspective on Yuu'. In this story, it's told from Shinoa's point of view, which gives a deeper understanding of her feelings for Yuu. It shows her internal struggles as she tries to come to terms with her growing affection while also dealing with the chaos around them.
One possible analysis could be that it allows for a more personalized take on the 'Owari no Seraph' universe. OC (original character) fanfictions often bring in new storylines and character dynamics. It might explore relationships between the existing characters in the series and the newly created OC in unique ways, such as a romantic relationship or a friendship that changes the course of the story.
It's mainly about the story in the 'Owari no Seraph' universe presented in a visual novel format. It likely involves the complex relationships between the characters, the battle against vampires, and the struggle for survival in a post - apocalyptic world.
One possible fanfic could be about Mika and Krul forming an unexpected alliance. Maybe they have to work together to face a common enemy that threatens both of their existences. In this story, Mika might start to see Krul in a different light, not just as a vampire but as someone with her own motives and desires.