Sakura might be really surprised at first. She could be a bit skeptical about whether it's really Naruto or some kind of trick. But then she would probably try to help him find a way to change back.
His friends' reactions could vary greatly. For example, Choji might be a bit scared at first, seeing Naruto as a wolf. But once he realizes it's still Naruto, he would offer him food. Ino could use her mind - transfer jutsu to communicate with Naruto in his wolf form. And Hinata would be very concerned and would stay close to Naruto, trying to protect him from any harm that might come his way because of his new form.
His friends' reactions would be mixed. Shikamaru would be like 'This is such a drag.' But he'd also start thinking of strategies to deal with the situation. Ino would be all about helping Naruto with his new look, like suggesting new outfits that would suit a fox girl. Choji would be more focused on making sure Naruto is still the same person inside. He'd offer Naruto his snacks to cheer him up. And Hinata would be blushing a lot, but also be very supportive, saying things like 'Naruto - kun, you look... different, but you're still you.'
It could be that Kurama's power goes out of control and accidentally turns Naruto into a fox girl. Naruto then has to search for a way to fix it. In the process, he might discover new aspects of Kurama's power. He could also meet some old enemies who don't recognize him in this new form and this could lead to some interesting encounters. Naruto would also have to deal with the cultural and social implications of being a fox girl in the ninja world, such as how he is treated differently by different clans.
Sakura might be initially shocked and a bit jealous at how cute Naruto - as - a - girl is. Sasuke would probably be confused at first but then act indifferent. Kakashi would be his usual calm self, but might crack a few jokes about Naruto's new look.
Sakura might be initially shocked. But being a good friend, she would quickly try to understand what happened to Naruto. She could offer to help him find a way to change back or support him in dealing with the new form. Sasuke, on the other hand, might be more aloof at first. He would see Naruto's transformation as a sign of weakness, but as time passes and Naruto proves his strength in the new form, Sasuke might start to respect him again.
Sakura might be a bit cautious at first. She'd worry about the fox being a danger or a distraction. But after seeing how Naruto cares for it, she'd warm up and might even help Naruto take care of it, like making sure it has proper food. Sasuke would probably be indifferent at first, but if the fox showed some useful skills in battle, he'd start to respect it. Shikamaru would just sigh and say it's too troublesome, but still offer some strategic advice on how to keep the fox hidden from enemies if needed.
Naruto would also have to deal with the physical differences. As a girl, she might not have the same physical strength she had as a boy. This could be a big issue in combat situations, as she would need to adapt her fighting style. Maybe she would have to rely more on agility and strategy rather than brute force.
Kurama might become angry at first. He's a powerful being and being neglected would likely wound his pride. He could start causing some minor disruptions inside Naruto, like making it harder for Naruto to access his chakra.
One main theme is often friendship. Kurama, being a powerful and somewhat solitary being, and the fox - girl, who may be an outcast in the Naruto world, can form a strong bond of friendship. Another theme could be power and its implications. Their combined powers can be used for good or bad, depending on how the story is written.
One popular Kurama Naruto Fox Girl fanfiction is 'The Fox - Spirit Bond'. It explores the unique relationship between Naruto and a fox - girl who has a connection to Kurama. The story is filled with adventure as they face various challenges together.