Definitely Ruby. She's the main character in RWBY, and Naruto would be drawn to her positive attitude and determination. They could learn a lot from each other. Naruto could teach her about the importance of never giving up like he did in his own journey, and Ruby could show Naruto how to use Dust.
He would interact with Blake. Blake has a complex backstory and is part of the faunus community. Naruto, who has his own experiences of being an outsider, would be able to relate to her. They might have deep conversations about acceptance and fighting for what's right. Also, Naruto would probably meet Yang, Ruby's sister. Their energetic personalities might clash at first, but then they'd become good friends and sparring partners.
Ruby Rose for sure. She's the main character in Remnant and Naruto would likely be drawn to her energy and determination. He could also interact with Weiss Schnee. Naruto might be interested in her family's power and wealth, and Weiss could be curious about Naruto's strange abilities. Another one could be Blake Belladonna. Given her past and her more reserved nature, Naruto might try to befriend her and help her open up more.
I think Naruto would interact a great deal with Hinata. Hinata has had a crush on Naruto for a long time. In Team 8, she might be more open with her feelings. Naruto, being kind - hearted, would notice her kindness towards him. They could have some sweet moments together while also training and going on missions as part of the team.
In this fanfiction, Naruto would interact with Vesemir, the old and wise Witcher. Vesemir could see Naruto's potential and help him understand the history and traditions of the Witchers. Naruto would also run into the various monsters in the Witcher world. Instead of just fighting them right away, he might try to communicate with them first, like he did with some of the tailed beasts in his own world. His interactions with these creatures would be unique and could even change the way Witchers view certain monsters.
He would surely interact with Harry Potter. They could share their experiences of being the main defenders in their respective worlds. Naruto might also interact with Dumbledore. Dumbledore would be interested in Naruto's unique abilities and Naruto would respect Dumbledore's wisdom.
He would likely interact with the Dragonborn. They could have an interesting exchange of skills, with Naruto showing off his Rasengan and the Dragonborn demonstrating shouts. He might also meet the various Jarls in the different holds, trying to understand their leadership styles which are different from the Hokage in Konoha.
The main character is Naruto, who is in the Remnant world. In addition to him, there could be some original characters created specifically for this fanfiction. They might be characters who are influenced by Naruto's presence in their world. Maybe a young trainee who idolizes Naruto and tries to learn from him, and this character could play a crucial role in the story along with Naruto and the RWBY characters.
He would be protective of the cat. Given his nature of always wanting to protect the weak, if any threats came towards the cat, Naruto would be the first to step in. He might also talk to the cat a lot, sharing his dreams and stories about his adventures, even if the cat couldn't understand his words.
He would probably interact with the Hogwarts professors. For instance, he could have discussions with Dumbledore about different forms of power - his ninja chakra and Hogwarts magic. He might also work closely with McGonagall, who could be interested in Naruto's shape - shifting abilities compared to her Animagus form.
Ruby Rose for sure. They both have a strong sense of justice and a desire to protect others. Naruto would be intrigued by Ruby's scythe and her use of Dust. And Ruby would be interested in Naruto's ninja tools and jutsu.
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.