They would probably start by catching up. Naruto has a lot of adventures, and his sister would be eager to hear about them. They would talk and laugh, reminiscing about old times.
There could be some sibling rivalry too. They might compete in small things like who can climb a tree faster or who can make a better clone. But it would all be in good fun, and in the end, it would strengthen their bond as siblings.
Naruto might be protective of his sister. He has a big heart, and being alone with her, he would make sure she is safe. He could be on the lookout for any potential threats while they are together. His sister, in turn, might be a bit more relaxed knowing Naruto is there to protect her.
Perhaps they would explore their family secrets. Since Naruto has always been in the dark about some aspects of his family, with just the two of them, they could start looking into old family mementos or stories that might lead to uncovering hidden truths.
The relationship could start with Naruto being overly protective of his sister, but she wants more independence. This causes friction. Later, when she gets into trouble that only Naruto can help her with, he steps in. This makes her realize that his over - protectiveness comes from love, and they begin to repair their relationship. For instance, if she is kidnapped by a powerful enemy, Naruto uses all his skills to rescue her, and during this process, they have heart - to - heart conversations.
Naruto would probably be very curious about the twin sister. He'd be friendly and try to make her feel welcome. Elsa - like powers would amaze him. Haku, being more reserved, might be cautious at first. But as he sees the sister's good intentions, he'd warm up. The twin sister would likely be a bit confused at first in this new world. She might look to Haku for some stability as he seems to have a calm presence.
The characters from Harry Potter and Naruto would interact in interesting ways. For instance, Hermione might be fascinated by the ninja techniques and try to study them. Naruto, as her brother, would be very protective of fem Harry. He would introduce her to his friends like Sasuke and Sakura, and there could be some initial misunderstandings because of the different cultures.
Since Naruto has the Nine - Tailed Fox's chakra, there could be a scenario where the powerful and chaotic chakra somehow affects Azula's firebending. It could make her flames even more intense but also more difficult to control. On the other hand, Azula's precise control over fire could potentially help Naruto in learning better chakra control for his more powerful jutsu.
It could bring them closer. Having to learn and speak English together would mean they rely on each other more. They would share the struggles and the joys of mastering a new language, which would strengthen their bond.
In some fanfictions, they interact more like true siblings. Naruto might be overly protective of Sasuke, and Sasuke could be more open with his feelings towards Naruto. For example, Sasuke might share his insecurities about his clan's past with Naruto more freely.
Naruto would use his ninja skills. He might start with a diversion, like creating some clones to distract the assassin while he gets his sister to a safer place.
Naruto's love for his sister would probably add a new layer of complexity to his character. On one hand, he would be the strong and fearless ninja. But on the other hand, he would have a soft spot for his sister. This could lead to some internal conflicts. For example, if he has to choose between a mission for the village and protecting his sister. It would also force him to grow in terms of his decision - making skills and his ability to balance different aspects of his life.
Naruto would probably be very cautious around Aizen at first. He's used to facing powerful enemies, but Aizen's deceptive nature would be a new challenge. Aizen, on the other hand, might see Naruto as an interesting specimen, someone with a strong will and great power that he could potentially manipulate.