One possible storyline could be that Yui discovers she's pregnant and has to deal with the mixed reactions of the Diabolik Lovers boys. Some might be possessive and overprotective, while others could be more indifferent or even see it as a way to further manipulate her. The pregnancy could also bring out a more vulnerable side of Yui as she faces the uncertainties of motherhood in such a strange and often hostile environment.
One great fanfic you could look for is 'A New Beginning for Ayato and Yui'. It beautifully explores their relationship after Yui discovers she is pregnant. It delves into how Ayato, who was initially shocked, gradually becomes a very protective and loving partner. The story also shows Yui's strength as she prepares for motherhood in such a complex world of Diabolik Lovers.
It would likely create a lot of chaos. The vampires are used to having control over Yui, but a pregnancy would shift the power dynamics. Yui would have a new focus - her unborn child - which could make her more assertive. The vampires would either have to adapt or try to regain control. For example, if one of them is the father, he might become more possessive, while the others could be jealous or feel left out.
One great fanfic could be where Yui and Ayato go on an adventure outside the Sakamaki mansion. They might encounter some other supernatural beings and have to rely on each other to survive. Ayato could show his protective side towards Yui in a more dangerous and unfamiliar setting.
In a fanfiction, Yui and Ayato could go on an adventure together. They might find themselves in a mysterious part of the mansion that no one has explored before. As they face various challenges there, they have to rely on each other. Ayato, who is usually so self - assured, might start to see Yui in a new light as her bravery and determination shine through.
One possible plot could be that Yui discovers a long - forgotten part of Shu's past. Maybe she stumbles upon an old diary in the Sakamaki mansion that reveals some deep - seated fears or dreams of Shu's from his human days. As she tries to understand him better through this discovery, their relationship deepens in a more profound and emotional way.
One idea could be that the female OC is a new student at the school. She has a special power that she doesn't fully understand yet. Yui befriends her, and together they try to figure out the secrets of the Sakamaki brothers. The OC's power might attract the brothers' attention in different ways, some being more menacing and some being more curious.
One possible plot could be that Yui discovers she's pregnant and is filled with a mix of fear and joy. Ayato, initially shocked, then becomes overprotective. They might face challenges from the other vampire brothers who are either jealous or worried about the implications. Yui would have to deal with her changing body while also trying to fit into the dangerous vampire world. Ayato could struggle with his own vampire instincts and how to be a good father figure.
Another theme is Yui's struggle to adapt to Kanato's ways. Yui is usually portrayed as a more innocent character, and in the relationship with Kanato, she has to deal with his erratic behavior and the overall dark and dangerous environment of the Diabolik Lovers world. So many fanfics focus on her journey in this regard.
Love and redemption are common themes. Usually, Subaru has a tortured past and Yui's love is seen as a way to redeem him. For example, in many fanfics, Yui's kindness slowly breaks through Subaru's tough exterior.
A common theme is the struggle for independence within the relationship. Yui may strive to maintain her own identity while being in a relationship with Ayato. Also, the idea of redemption can be a theme. Ayato, as a vampire with a sometimes dark nature, may seek redemption through his relationship with Yui. And of course, the theme of forbidden love, given the differences between a vampire and a human, is very common in 'diabolik lovers ayato x yui fanfic'.