One thing that makes this type of fanfiction appealing is the contrast. Naruto, a character known for his loyalty, is betrayed in his own world. Then he's thrown into the DxD highschool where there's a whole new set of rules and relationships. The harem part means there are multiple characters with different personalities that can have various interactions with Naruto. It's also about seeing Naruto grow and change in this new environment, perhaps learning to trust again through his relationships with the harem members.
One common theme is redemption. Naruto, after being betrayed, often seeks to redeem himself or prove his worth in the eyes of others, especially the females in his harem. Another theme is trust. Since he was betrayed, rebuilding trust becomes crucial in his relationships with the harem members.
Well, Mirajane could be part of the harem. She has a motherly side and would want to comfort Natsu if he was betrayed. Levy is also smart and resourceful, and she could use her skills to help Natsu out. Juvia, with her obsessive love for Gray, might transfer some of that intense loyalty to Natsu if she saw him in a desperate situation after being betrayed.
In a 'Naruto betrayed harem fanfiction', it could be that Naruto is blamed for something he didn't do within the harem. For example, a valuable item goes missing and the harem members quickly point fingers at Naruto. They don't believe his innocence and start to shun him. Naruto then realizes that these people he thought were his friends in the harem are not so trustworthy after all, and thus he experiences betrayal.
In a Naruto betrayed by everyone harem fanfiction, the plot might start with Naruto being framed for a major crime against the village. The harem elements could be that his so - called harem members, who are usually his friends and admirers, are caught in a dilemma. They love Naruto but the evidence against him seems overwhelming. As the story unfolds, Naruto may have to fight not only to clear his name but also to win back the trust of his harem. It could involve him going on a journey to find the real culprit while facing the animosity of his former friends and the village he once loved.
It could be one of the harem members who has a hidden dark side. Maybe she's jealous of Naruto's closeness to others in the harem and decides to turn the rest against him, so she becomes the main antagonist.
It could be a new character, someone who is jealous of Naruto's growing power and popularity among the girls. This person might spread false information to turn everyone against Naruto. Maybe a rogue ninja who has infiltrated the village and has a vendetta against Naruto for some unknown reason.
Sakura could be in the harem. She has a long - standing relationship with Naruto in the original series, and in this fanfiction, his Saiyan powers might make her see him in a new light. Hinata is also a likely candidate. Her admiration for Naruto could turn into a deeper relationship given his Saiyan - like abilities.
One idea could be that Natsu is betrayed by his closest friends in the guild, and in his time of despair, a group of female characters form a harem around him to help him heal and regain his confidence. For example, Lucy could be the first to reach out, using her celestial magic to show him there are still things to fight for. Another plot could involve Natsu being betrayed by a powerful dark mage who manipulates his guild against him. The harem, which might include Erza, Wendy, and others, then trains Natsu in secret to become stronger and take revenge on those who wronged him.
Sakura could be one of the members. She has always had a complex relationship with Naruto. In this harem scenario, her feelings could evolve further. Hinata is also a likely candidate. Her long - standing admiration for Naruto might lead her to be part of the harem. Tenten could also join, perhaps drawn in by Naruto's growth as a ninja.