The Anbu sister could be a powerful and mysterious character. In the fanfiction, she might have unique abilities that Naruto is curious about. Their meetings could be filled with tension at first, as the Anbu are often secretive. But as Naruto's friendly nature breaks through, they start to share their stories.
One possible fanfiction could be about Naruto forming an unexpected bond with Kurenai's sister who is in the Anbu. Maybe Naruto stumbles upon her during a mission and they start to work together, gradually learning about each other's pasts and dreams.
For Kurenai, her character could be developed by exploring her relationships with other members of the village more deeply. For example, showing how she mentors the younger generation in addition to her regular duties. In the context of ANBU, she could be given a role where she has to train some of the ANBU recruits. As for Naruto, if he is involved, his time in the ANBU could show his growth in stealth and strategy, which are different from his usual combat style.
It would be more nurturing. Kurenai could cook for Naruto, like making him some of her special ninja - style meals. And she'd be there to listen to his problems, whether it's about his love life or his struggles with mastering new jutsu. Their relationship would be based on mutual trust and respect, just like a real sister - brother relationship.
Another idea is a story where Naruto joins the ANBU and is paired with Kurenai for a special undercover operation. They have to infiltrate an enemy organization that is suspected of planning an attack on Konoha. Along the way, they learn more about each other's pasts and develop a strong bond as comrades.
Well, it could be about Kurenai having some secret connection to Naruto as his sister. Maybe she discovers this truth and has to deal with the implications. For example, she might have to protect Naruto from new threats while also coming to terms with her new - found family relation.
The Akatsuki could be the main antagonists. Since Naruto is an important target for them, and if Kurenai is now his sister, they might see her as an obstacle in their way. They could try to use their various powers and strategies to either capture Naruto or cause harm to both him and Kurenai.
Naruto would probably be initially cautious but also curious. He has a knack for seeing the good in people, so he might try to befriend the Akatsuki sister. Kurenai, on the other hand, would be more guarded. She is a more experienced ninja and would be wary of any Akatsuki member. But she also might see an opportunity to gain intel from the sister.
One possible storyline could be a story of friendship and alliance. Maybe Naruto and Kurenai team up with an Akatsuki sister who has a change of heart. They could fight against the more evil elements within the Akatsuki together.
Well, it could be about Kurenai taking on a sisterly role for Naruto. Maybe she helps him train, like teaching him some special genjutsu techniques that she's good at. She could also be there to support him emotionally, especially when he faces difficulties in the village or in his ninja missions.