Naruto might be initially surprised. He's always seen Hanabi as Hinata's little sister. So, he could be caught off - guard by her feelings.
The Hyuga clan members would be very confused by 'Hanabi' (really Naruto). They would notice her (his) un - Hyuga - like behavior and attitude. For example, Naruto's loud and friendly nature would be a stark contrast to Hanabi's more reserved Hyuga self. As for Naruto's friends, they would be puzzled by 'Naruto' (actually Hanabi). They would wonder why he (she) seems a bit different in combat and decision - making.
Well, Hanabi falling in love with Naruto could also lead to some interesting interactions with her sister, Hinata. Since Hinata has her own feelings for Naruto, there could be some sisterly drama. Hanabi might feel guilty about her feelings for Naruto at first, but then realize that she can't control who she falls in love with.
In this fanfiction, Naruto's personality could shift in a few ways. He'd likely become more attuned to the needs of the Hyuga clan, trying to fit in and understand their ways. His impulsiveness might be tempered a bit as he has to consider Hanabi's feelings and the traditions of her family. Hanabi would change too. She'd become more flexible, learning from Naruto's ability to adapt to different situations. Her quiet nature could gain a bit of Naruto's boldness, and she might be more willing to speak up for what she believes in, especially when it comes to their relationship.
Often, Hinata might be included. Since Hinata has a long - standing relationship with Naruto in the original series, in a harem fanfiction, she could be part of the group. Also, Sakura could be there. She has her own complex relationship with Naruto in the original Naruto story, so it makes sense for her to be in a harem setting with him in fanfiction. Another character could be Ino. She is also a female ninja who has interacted with Naruto and could potentially be part of this harem scenario.
In the fanfiction, a big challenge could be the jealousy or interference from other characters. There might be other people who have feelings for Naruto or Hanabi. For Naruto, Sakura might still have some unresolved feelings, and she could potentially cause some problems for their relationship. For Hanabi, there could be members of the Hyuga clan who oppose her being with Naruto, thinking that he is not a suitable match for her in terms of clan traditions and politics. All these factors combined would create many challenges for Naruto and Hanabi to overcome.
Hinata might be a bit surprised at first. Since she also has feelings for Naruto, she could feel a bit of jealousy. But being the kind person she is, she would probably try to be understanding and not let it affect her friendship with Hanabi.
Naruto's character could develop by becoming more protective. After saving Hinata and Hanabi, he might realize how much they mean to him and the village. This could make him more vigilant in looking out for threats against them and the rest of the clan.
Hinata would probably be very shocked at first. Since she has feelings for Naruto as well, she might feel a bit betrayed but also happy for her sister. She would be in a very conflicted state.
Yes, there are some. You can check out fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'naruto and hanabi love' and you'll find a variety of stories, but the quality may vary.
Common themes include the idea of forbidden love in some cases. Given their different clans and positions within the ninja world, it can be seen as something that goes against the norm. Also, there are themes of mutual growth. As they get closer, they help each other become better ninjas, both in terms of skills and in understanding their own emotions and responsibilities.