What are some interesting plot ideas for 'a devil is unbreakable fanfiction'?

One idea could be Percy using his devilish powers to protect his friends in a unique way. Maybe he has the power to manipulate shadows and uses this to create illusions to mislead enemies.

One idea could be Naruto discovers a hidden realm where devil hunters operate and he has to learn their ways to save his village from a devil invasion.

One interesting plot idea could be a crossover between the Devil May Cry universe and the Castlevania universe. The protagonist with Devil Trigger ability could find himself in the dark and haunted world of Castlevania. He has to use his powers to fight off the hordes of demons and undead creatures that are native to Castlevania. Maybe he teams up with a Belmont character and they exchange combat techniques and knowledge about their respective worlds.

One idea could be a story where Dante discovers a hidden demonic realm within the human world that has been influencing events without his knowledge. He has to team up with a new, inexperienced hunter to navigate this strange place.

Maybe an OC devil who was once a human and was turned into a devil against their will. They could struggle with their new identity while still having some human emotions, which would create complex relationships with the Hellsing characters.

One idea could be to have characters from different universes within the 'devil survivor 2' world meet and form unexpected alliances. For example, a group of normally opposing demon summoners having to work together to face a greater threat that endangers all of their worlds.

One idea could be a new devil character arriving at Kuoh Academy with a unique power that challenges the existing power dynamics among the devils there. For example, a devil who can manipulate time in small increments during battles, which would make for some really intense and strategic fight scenes.

One interesting plot idea is Izuku inheriting some of Dante's powers. For example, he could gain the ability to use Devil Arms and his combat skills could be enhanced in a unique way. Another could be Izuku getting involved in the demon - hunting world of Devil May Cry while still trying to be a hero in his own world. It would be a cool mix of the two universes.

One idea could be a story where the main character, a human, discovers a unique power that allows them to hold their own against devils in the 'Highschool DxD' universe. They use this power to protect their school from devil threats that the regular characters might not be able to handle easily.

One idea could be an OC who is a descendant of a powerful demon slayer family. They come to the world of Devil May Cry with unique weapons and skills, and have to team up with Dante and the gang to face a new, super - powerful demon threat. Their family's secrets and ancient techniques add new twists to the story.