They could start by having some friendly competitions. For example, in a race to the top of a mountain or a sparring match. This would not only show their bond but also their competitive nature as siblings.
It's completely unacceptable. Naruto is a well - loved anime with a large and diverse fanbase. The idea of a relationship between Naruto and his twin sister in a 'lemon' (usually implying sexual content) way is not only against the ethics of the Naruto world but also goes against basic moral and family values. It would be seen as a perversion of the characters and the story by most fans.
At first, the relationship might be strained. Naruto could be jealous of his sister's favored status. However, as the story progresses, his sister might start to see the injustice Naruto faces and try to bridge the gap. They could gradually develop a more understanding and loving relationship.
In a Gaara x Naruto twin sister fanfiction, their relationship might develop slowly. Gaara, with his past traumas, would be cautious. The sister, perhaps having grown up in the shadow of Naruto, has her own insecurities. Their connection could be based on mutual understanding of being outsiders in a way. They might bond over shared experiences that Naruto doesn't fully understand.
First, give her a distinct personality. If Naruto is all about determination and Sasuke is brooding, she could be the calm and wise one. Then, give her a backstory. Maybe she was separated from Sasuke at a young age and grew up in a different part of the ninja world. This would shape her view of things. Another way is to show her relationships. For example, how she interacts with Naruto's friends like Sakura and Kakashi. This will help to flesh out her character more.
One idea could be that the twin sister has a unique power that Naruto doesn't have, like the ability to communicate with animals on a deeper level. This power could help them in their adventures, for example, when they are trying to find a missing ninja. The sister could use her animal friends to track the missing person.
In the original Naruto story, there are no such inappropriate relationships or sexual undertones. Naruto is busy with training, facing challenges in the ninja world, and building relationships with his peers. A 'Naruto x His Twin Sister Lemon' fanfiction strays far from this. It not only introduces an incestuous relationship but also sexual content which is completely against the family - friendly and adventure - based nature of the original Naruto. It changes the focus from Naruto's heroic journey to something that is not acceptable in the context of the Naruto world.
One possible plot could be that Naruto's twin sister has a unique and powerful ninja ability that she has to keep hidden from the village at first. Maybe she can communicate with animals in a very special way, like having full conversations and understanding their emotions. As the story progresses, she uses this ability to help Naruto and their friends in various missions, for example, finding a lost ninja by asking the birds for directions.
In a 'naruto meets his twin sister fanfiction', perhaps his sister has been living in a different village all this time. When they meet, she could be a very powerful ninja in her own right. Their meeting could stir up a lot of emotions, like Naruto feeling a sense of family he's never had before. They might team up to face a common enemy, using their shared bloodline abilities in unique ways.
Often, there are plotlines centered around the sister's role in Naruto's growth. She might be the one who encourages him to master a new technique or helps him deal with his inner demons. In other cases, the twin sister is kidnapped or in danger, and Naruto has to go on a rescue mission. This not only shows their bond but also gives the opportunity for action - packed scenes. There are also fanfictions where the sister has a hidden power that is linked to Naruto's own power, and they have to figure out how to use it together.