One plotline could be Naruto teaching his sister ninjutsu. Since Naruto has his own unique skills like the Rasengan, he could pass on some basic forms of it to his sister. Another could be Naruto protecting his sister from the village's initial distrust, just as he faced it himself. Maybe he has to stand up to the village elders to ensure his sister gets a fair chance at becoming a ninja.
Perhaps Naruto's sister has a special power that she struggles to control. Naruto, having faced his own challenges with the Nine - Tails' power, could be there to support her. He could take her to different mentors in the village to help her master her power. And as she grows, they could team up for missions, with Naruto always looking out for her and teaching her the importance of teamwork and loyalty.
One possible plotline could be Iruka and Kakashi trying to teach Naruto different ninja skills in their own unique ways. For example, Kakashi might focus on more advanced combat techniques while Iruka helps Naruto with the basic ninja knowledge. Another plotline could be them dealing with Naruto's pranks and how they discipline him in a loving yet firm manner. Maybe they also have to protect Naruto from some of the more dangerous elements in the ninja world that target him because of his status as the Jinchuriki.
Another plotline could involve the adopted sister coming from a different village and having a hard time adjusting to life in Konoha. Naruto, having been an outcast himself, can relate to her struggles. He shows her around, introduces her to his friends, and they gradually form a strong bond as she starts to feel at home.
In a Naruto - raises - Gaara fanfiction, Naruto could help Gaara deal with his inner demon. Gaara has had a tough time controlling Shukaku, his tailed beast. Naruto, who has also had to deal with the power of the Nine - Tails, could offer advice and support. He might teach Gaara some of the meditation techniques he used to keep the Nine - Tails in check. This would lead to Gaara having better control over his powers and becoming a more stable and powerful shinobi. Also, Naruto could help Gaara improve his relationship with the people of Suna. Given Naruto's charm and ability to make friends, he could show Gaara how to win the trust and love of his own villagers.
Perhaps there could be a plot where Naruto's twin sister gets into some kind of trouble, like being kidnapped by an enemy ninja clan. Naruto then goes on a desperate mission to rescue her. During this time, he realizes just how much she means to him. He uses all his skills and the power of his friends to get her back, and in the end, their bond becomes even stronger.
One possible plotline could be that Naruto's family is in a difficult situation and they believe they can only support his sister. So, Naruto is left on his own. He then has to struggle to survive in the ninja world without the support of his family. He might become more independent and self - reliant, forging his own path.
One interesting plotline could be Thranduil teaching Legolas how to hunt. Thranduil, being a skilled hunter, would pass on his knowledge to the young Legolas. He could start with teaching him how to track small animals in the forest. Another could be about Thranduil introducing Legolas to the different cultures within their realm. This would help Legolas understand the various elves and their ways, which would be important for his future role as a prince.
One possible plotline could be Naruto teaching Anko some of his unique ninja skills. Since Naruto has a lot of experience with Rasengan and other techniques, he could pass on some knowledge to Anko, who might be struggling with her own skills development. Another aspect could be Naruto helping Anko overcome some personal traumas. Maybe Anko has some past experiences that are holding her back, and Naruto's positive attitude and his own history of overcoming difficulties could inspire her. Also, they could go on missions together where Naruto's quick - thinking and Anko's more experienced knowledge of certain areas combine to make them a great team.
One possible plotline could be Naruto's overprotective behavior towards his sister in the fanfiction. He might get into fights with anyone he perceives as a threat to her. For example, if a boy shows interest in his sister, Naruto could go all out to intimidate the poor guy, creating some comical and tense situations.
A great plotline could be Snape training Draco in advanced potions and magic that are not part of the regular Hogwarts curriculum. This could lead to Draco having unique skills that help him in the wizarding world. Also, Snape might take Draco on secret excursions to learn about the history of the Dark Arts in a way that doesn't lead him down a dark path but rather makes him understand the dangers better.
One idea could be that Harry discovers he has a sister he never knew about. He then has to protect her from the dark forces in the wizarding world while also teaching her about magic. Maybe they go on a journey to find out more about their family's past together.