Tsunade could be part of it. Since she is a Senju, she could be a powerful ally and also someone who helps Naruto and Hinata navigate the complex relationships in the harem. Also, Nawaki Senju could be brought back in some way, maybe as a spirit or through some time - travel plot device. He could befriend Naruto and be involved in the growth of the relationships within the harem.
There could also be some original characters created for the fanfiction. For example, a young Senju girl who has a crush on Naruto and causes some jealousy in Hinata. This would add more drama to the harem dynamic. Or an old Senju sage who appears to give Naruto and the harem members advice on how to balance their relationships and their duties to the village.
One idea could be Naruto, who has a connection to the Senju clan, finds himself in a harem situation with Hinata. Maybe they all have to go on a quest to protect the village, and during this journey, their relationships develop. For example, Hinata could use her Byakugan to help them avoid traps while Naruto uses his Senju - related powers to fight off enemies.
Sakura could be a common character. Since she has a history with Naruto, she might be part of the harem in some fanfictions. Also, Tenten could be included as she is another female ninja in the Naruto universe. And Ino, with her strong personality, could also be written into the harem scenario.
Obviously Naruto would be the main character. For the harem, it could include Sakura. She is strong - willed and her medical skills could be interesting in relation to Naruto's ghoul nature. Hinata is also a likely candidate. Her gentle and loving nature could contrast with Naruto's more dangerous ghoul side. And then there's Tenten, who could bring her weapon - using skills into the mix.
Obviously, Naruto himself as the lycan. Hinata could be one of the harem members as she has a long - standing crush on Naruto. Sakura might also be part of it, adding some tension due to her previous relationship with Sasuke. Then there could be Ino, who is strong - willed and could have an interesting dynamic with Naruto in this context. And Tenten, with her skills, could also be a part of the harem.
It's also possible that some non - human characters could be part of the harem. For example, some of the tailed beasts in human form (if that's possible in the context of the fanfiction). They would bring their own set of powers and a very different kind of relationship with Naruto compared to the human characters in the harem.
Well, Naruto himself is obviously a main character. As for the servants, Sakura could potentially be one. She has her own skills and a relationship with Naruto already in the original series that could be developed further in this fanfiction context. Hinata is also a likely candidate, given her long - standing feelings for Naruto.
Tenten could potentially be in the harem. She is a strong - willed and capable kunoichi. Her presence in the harem could add an element of action and adventure. Maybe she initially tries to fight against the evil Naruto but then gets drawn into his world and eventually becomes part of his harem.
There could be some original Arrancar characters created specifically for the fanfiction. For example, a young and curious Arrancar who is new to the ways of her kind. She meets Naruto and is immediately fascinated by his different appearance and abilities. And then there's a more experienced Arrancar who has seen many battles. She initially sees Naruto as a threat but then realizes his good intentions and slowly falls for him, becoming part of the harem.
I'm not entirely sure if it's a highly popular genre. While the Naruto fanfiction world is vast and diverse, the idea of a'slave harem' concept might not be as mainstream as other themes like adventure or character development. It could appeal to a niche group who are interested in exploring such unique and often controversial relationship dynamics within the Naruto universe.
In the Naruto world, Sakura could be a potential character in the harem. She's strong - willed and has her own set of skills. From the Yugioh world, Anzu could be part of it. She's kind - hearted and often supports the main characters. Another from Naruto could be Hinata, who is shy but also very loyal. And from Yugioh, Mai Valentine, as she has a bold and confident personality.