One possible plot could be that Natsu, being in the DxD High School setting, is betrayed by someone he considered a close friend. Maybe this friend reveals Natsu's secrets to the enemies in the DxD world. As a result, Natsu has to face new challenges alone, all while trying to figure out how to deal with the betrayal and regain his trust in others.
Well, perhaps Natsu is betrayed when he's on a joint mission in DxD High School. His teammate might leave him in a dangerous situation. Natsu then has to find his way out and also has to deal with the emotional turmoil of the betrayal. He could start to question his own judgment in trusting people and might become more guarded in future interactions.
In a DxD High School fanfiction with a betrayed Natsu, it could start with Natsu being excited to be in this new and different world. But then, someone he trusts, like a fellow student, betrays him by spreading false rumors about him. This causes Natsu to be ostracized by some of the students. He has to fight not only against the social isolation but also against any potential threats that come his way because of the rumors. Natsu's character could develop in a way where he becomes more self - reliant and less quick to trust, which would be a big change from his usually trusting nature in his original setting.
Well, one possible plot could be that Natsu is betrayed in his own world and somehow ends up in the DxD Highschool universe. Maybe he has to deal with the different power dynamics and politics there while also trying to figure out who betrayed him in his original world. He might form new alliances with the characters in DxD Highschool and use his unique abilities to survive and seek revenge for his betrayal.
It could be Issei. Maybe he becomes jealous of Natsu's power or popularity in DxD High School and decides to betray him for his own gain.
One possible fanfiction idea could be that Naruto, who somehow ends up in the world of High School DxD, is betrayed by some of the devils there. Maybe they initially seem friendly but then backstab him for his power or because they fear his potential. Naruto, being the resilient character he is, would then have to find a way to overcome this betrayal and prove himself.
One possible plot is that Gilgamesh views the High School DxD setting as beneath him at first. But as he gets to know the characters like Issei and Rias, he starts to see the value in their struggles. He could then use his vast resources and power to help them in their fight against stronger enemies, all while maintaining his haughty and kingly demeanor.
Well, the plot could involve Shirou and Artoria being transferred to the High School DxD world. Maybe they would have to deal with the devils, angels, and fallen angels there. Shirou's combat skills and Artoria's power would surely make an impact. They could form alliances or even find themselves in the middle of the three - faction conflict.
Well, it could be about the Son of Amaterasu having to deal with the power struggles in the High School DxD world. Maybe he has some unique abilities inherited from his mother that make him a target or a valuable ally.
The plot could also be centered on a mystery related to their family. The brother of Rias discovers some secrets about their family's past that put them both in danger. He then has to work with Rias to uncover the truth and stop whoever is trying to use their family secrets against them. This could involve battles, political intrigue within the Devil world, and self - discovery for both of them.
Well, perhaps Erza was tricked into believing something false about Natsu. Maybe she was misled by some enemy who made it seem like Natsu was going to endanger the guild. So, in her sense of duty to protect the guild, she took actions that Natsu perceived as betrayal.
Perhaps she is betrayed in a romantic sense. She falls for someone who then turns out to be using her for their own gain, like getting closer to powerful members of the guild through her. This would shatter her trust in love and make her more guarded in future relationships.
The plot might involve Natsu being the popular jock type and Lucy the smart, bookish girl. They could initially clash but then realize they have feelings for each other. For example, Natsu might accidentally ruin Lucy's science project, but then he helps her rebuild it and that's when their relationship starts to change. They could go on to face challenges together like dealing with mean classmates or difficult teachers while also exploring their new - found love.