A fanfic could focus on the backstory of the Kamishiro brothers. Explore their childhood, how they discovered their powers, and what led them to become who they are. Maybe there was a tragic event in their past that shaped their personalities and made them so close to each other.
I think a 'brother to lover' fanfiction about Rize Kamishiro might explore complex emotions. It could delve into the initial bond of brotherhood and how it gradually transforms into romantic love. Maybe it would show their internal struggles as they deal with this shift in feelings, especially considering the social taboos often associated with such a relationship in many cultures.
First, know the characters well. Study their personalities, motives, and relationships in the original work. This will help you write them in a way that is consistent. For example, if one brother is more impulsive, show that in your fanfic.
Rize's older brother, Takumi, was different from the other Kamishiro family members. While Rize was known for her alluring and dangerous nature, Takumi was more of a thinker. He spent his days researching about the ghoul society, trying to find a way for ghouls and humans to coexist. He was often in his study, surrounded by old books and papers. But when it came to Rize, he was always there for her. He would listen to her problems, whether it was about her struggles with her ghoul instincts or her difficulties in dealing with other ghouls in the area.
There could be a fanfiction where Tsukushi and Tsukasa are expecting a child. It might explore how they prepare for the new arrival. For example, they could be shown shopping for baby clothes and setting up a nursery. The story could also delve into their emotions, like Tsukushi's excitement and Tsukasa's nervousness about becoming parents.
One aspect that could make it appealing is the exploration of deep emotional connections. Moving from a brotherly bond to a romantic one involves a whole range of emotions like confusion, guilt, and ultimately, deep love. The 'OC' in the fanfiction can also introduce fresh perspectives and storylines that can enhance the overall allure of the narrative. It allows for creativity in how the relationship unfolds and how the characters interact with this new situation.
In the fanfic, Rize and her older brother had a complex relationship. Her brother was always looking out for her. He was like a shadow, silently protecting her. Rize, on the other hand, sometimes resented his over - protectiveness. But deep down, she knew he was the only one she could truly trust. They shared a bond that was unbreakable, forged through the hardships of being ghouls in a human - dominated world.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfics from various fandoms, and there's a good chance you'll find some great anzai and tsukasa fanfics there.
Another theme can be personal growth. In many fanfics, both Tsukasa and Tsukushi might face difficulties that force them to grow and change. They support each other during this process, which is a great aspect of these stories. For example, Tsukasa might be shy at first but becomes more confident with Tsukushi's encouragement. Tsukushi, on the other hand, might learn to be more patient or understanding through their relationship.