One common theme is the exploration of their forbidden love. Since there are often barriers in their relationship, it makes for a very intense and emotional theme.
Another theme is the transformation of their characters through their relationship. As they interact more in these fanfics, they often grow and change. For example, Zero might become more open and Yuki more confident. It's about how their love affects who they are.
Another theme is the power of friendship turning into love. They start off as comrades or friends perhaps, and then the story shows how their relationship deepens into something more romantic. For example, in some fanfics, they go through adventures together which bring them closer and closer until they realize their true feelings for each other.
One common theme is the exploration of their complex relationship. Given their characters' backgrounds and the story's context, many fanfictions delve into how they interact with each other, the unspoken feelings, and the conflicts that arise from their different natures.
One common theme could be conflict. Since it's 'yuki hurts zero', there might be some sort of emotional or physical conflict between the two characters.
One common theme is the struggle between their different natures. Yuki might be seen as more innocent and Zero as more brooding, and the kiss can be a moment of breaking down those barriers. Another theme could be forbidden love, as there might be reasons in the story's universe that make their relationship difficult.
Love and sacrifice are common themes. Their relationship is often portrayed as a complex one where they are willing to sacrifice for each other. For example, Zero might sacrifice his own safety for Yuki.
Often, there could be a theme of redemption or growth. Zero and Yuki may have made mistakes in the past or had their own personal issues. In the married fanfiction, their relationship could be a catalyst for their individual growth. For example, Zero might learn to be more open and trusting, while Yuki could become more confident in her decisions. This growth can strengthen their marriage and make their relationship more fulfilling.
The theme of identity is also prevalent. Zero is constantly trying to figure out who he is now that he is part vampire. Yuki too has an identity crisis as she is caught between the human and vampire worlds. Fanfictions often delve into how they come to terms with their new identities, whether they accept them or try to change them, and how it affects their relationship with each other and those around them.
Since I don't have extensive knowledge of 'aido and yuki lemon fanfiction' in particular, generally in fanfictions related to characters, themes of self - discovery, relationship development, and overcoming challenges can be common. It's possible that in 'aido and yuki' fanfiction, their unique relationship dynamics might lead to themes around loyalty and mutual support.
One common theme could be friendship. Their relationship might start as a friendship and then develop into something deeper in the fanfiction. Another theme might be self - discovery, as they explore their own feelings towards each other.
Often, self - discovery within their relationship is also a theme. As they explore their feelings for each other on a deeper level in the fanfiction, they may also discover new aspects of themselves. This can be shown through their interactions, both in terms of dialogue and physical contact, which are often emphasized in 'lemon' fanfiction to create a more engaging and emotional story.