She could be a half - blood like Harry. Maybe her mother was a muggle - born witch and her father was a pure - blood wizard. This mixed heritage could give her a unique perspective on the wizarding world's issues regarding blood purity.
Some characters might become more protective of Takemichi if the fanfiction shows him in a difficult situation. They would feel a stronger bond towards him, wanting to ensure his safety. However, if the fanfiction distorts Takemichi's character too much, it could cause some confusion and even a bit of a rift. They might start to question if they really know Takemichi as well as they thought.
Maybe an original character could be created. This sister could be a powerful and wise ninja who has been traveling the world. She comes back to the village just in time to take Naruto under her wing. She could have a special kekkei genkai that she helps Naruto understand and perhaps develop in himself.
In bonten x takemichi fanfiction, the story could revolve around Takemichi trying to reform Bonten. He has a history of going back in time to change things, so it would be interesting to see him use his unique ability within the context of dealing with Bonten. It could also be about a relationship, not necessarily romantic, but one where Takemichi becomes a sort of moral compass for the group, and they in turn protect him from other threats in their dangerous underworld.
In Takemichi x Mikey fanfiction, a common theme could be their growth together. Takemichi's time - leaping ability can create really interesting storylines in relation to Mikey. For example, Takemichi might use his power to save Mikey from a dark future, and in the process, their relationship evolves. It's also possible that the fanfiction shows their shared dreams and how they strive to achieve them side by side.
I recommend 'One Child, Three Treasures, State Preceptor's Father Don't Think of Running Away' to you. The plot of this novel is similar to what you described. The novel told the story of two sisters. The elder sister was a cruel and money-loving person, while the younger sister was a muddle-headed person. In the end, the younger sister married the older sister's boss, and the older sister had no choice but to marry a silly boy. I hope you like this fairy's recommendation. Muah ~😗
Having sex with an older sister is completely unethical and goes against moral and social norms in almost all cultures. Incestuous relationships are not acceptable as they can cause a great deal of emotional and psychological harm to family members and violate the basic principles of family boundaries.
Yes, there are RWBY fanfictions where Ruby is the older sister. This can lead to interesting storylines. For example, it might change the dynamic between her and the other characters. She could be more protective or take on different leadership roles within the group. It also allows for exploring different family - related plotlines and character developments that might not be present in the original series.