Naruto and Rias are the central characters. Naruto is known for his never - give - up attitude and his array of ninja techniques. Rias is a complex character with her own political and social standing in the devil world. However, in some fanfictions, other characters from both the Naruto and High School DxD universes can become important. Kiba from Naruto might befriend Naruto in the new world and help him understand the devil society better. And from the High School DxD side, Akeno, Rias' friend, could play a role in either supporting or testing Naruto's relationship with Rias.
Naruto and Rias are bound to be the central characters. Naruto with his determination and power, and Rias with her leadership and magic. But we can't forget about the other members of Rias' peerage. They might have different reactions to Naruto being adopted. Some could be welcoming, while others might be a bit skeptical at first. And Naruto's own comrades from Konoha might also be relevant, perhaps in flashbacks or if they somehow cross over into Rias' world.
The two main characters are Naruto and Rias. Naruto, with his ninja skills and his journey of growth in his original story. Rias, whose actions towards Naruto are the central focus of this fanfiction. There could be side characters like Naruto's friends from his world who might try to find out what happened to him, or characters related to Rias who could either support or oppose her decision to leave Naruto to die.
The main characters are Naruto and Rias. Naruto is known for his rasengan and his ability to make friends and inspire those around him. Rias, on the other hand, is a leader among devils and has a group of loyal servants. In this fanfiction, with Rias being pregnant, their relationship and how they handle this new situation become the central focus of the story.
The main characters are Naruto and Rias. Naruto is the godlike character. His role is often to be the overpowered force that challenges or opposes Rias. He might use his incredible powers to put Rias in difficult situations. Rias, on the other hand, is the character who is often on the receiving end of Naruto's actions. She may be portrayed as an antagonist or at least someone who has to deal with Naruto's godlike presence.
The main characters are Ichigo and Rias. Ichigo is from the Bleach universe, a powerful Soul Reaper with unique abilities. He has a strong sense of justice and is always ready to protect those in need.
It could be Hinata. In the original series, Hinata has a deep affection for Naruto. In a fanfiction, it would be a natural progression for her to be his secret fiance. Maybe they got engaged secretly to avoid some political unrest in the village.
The main characters are Naruto, Rias, and Riser. Naruto is the savior. He comes from his own world of ninjas with his extraordinary skills and powers. His role is to rescue Rias from the clutches of Riser. Rias is the damsel in distress. She's in a difficult situation where she needs someone to save her from Riser. Riser is the antagonist. He's the one causing trouble for Rias and is the obstacle that Naruto has to overcome in order to save her.
Obviously, Naruto would be one of the main characters. He brings his ninja skills, his strong will, and his unique personality. And from the Rias family, Rias herself would be a main character. She has her own leadership within the family and her devil powers. Also, her peerage members could also be important characters as they interact with Naruto.
Rias herself could be the main antagonist in a way. Since she is the one neglecting Naruto, she stands in the way of Naruto's growth and acceptance in this new setting. Her actions and lack of recognition towards Naruto can be seen as antagonistic.
The main characters are clearly Rias and Issei. Rias is often a strong and important character in the series, and Issei is the one who hypnotizes her in this fanfiction.