What are some interesting ideas for a 'Highschool DxD Crossover Harem Fanfiction'?

A good concept for 'highschool dxd harem fanfiction' could be a time - travel story. The harem and Issei could be sent back in time and have to navigate the past while also dealing with their feelings for each other. They might meet younger versions of themselves or their predecessors. Another idea is to have a mystery element, where something strange is happening in the school and the harem has to solve it together. This could bring out different sides of each character and also develop their relationships further.

Maybe in the fanfiction, the Campione characters are invited to the Highschool DxD world to participate in a special tournament. They bring their own unique skills and knowledge, and during the tournament, they form unexpected alliances with the devils, angels, and fallen angels. This would allow for a lot of character interactions and development.

One idea could be that Naruto characters attend the Highschool DxD academy. For example, Naruto himself could be a new student with his unique ninja skills. He might form an unlikely friendship with Issei. Another idea is a battle tournament where ninja techniques are pitted against the devilish powers in the DxD world.

Maybe the story could revolve around the main character accidentally hypnotizing the wrong person in the harem, which leads to a series of comical and challenging situations. He has to then find a way to reverse the effects without causing too much chaos among the group.

Well, a plot could revolve around the main character getting sent on a special mission by the school's authorities. Along the way, he meets new female characters who end up joining his harem. Also, there could be a plot where the harem members start developing their own unique powers and they have to train together with the main character. This could strengthen their bonds not only as a harem but also as a team. And then, there could be a mystery element where someone is secretly trying to break up the harem, and the main character has to find out who it is.

One idea could be Gasper using his unique powers to protect his harem members from a new threat in the high school. Maybe a group of rogue devils tries to target the girls he cares about.

The OC could be a new transfer student with a mysterious past. As the story progresses, it's revealed that they are on a quest to find a powerful artifact that is somehow connected to the characters in the harem. This could lead to adventures together, and the building of deeper relationships within the harem.

Perhaps a plot where the members of Vali's harem start developing new and unique powers. They then have to train together to control these powers while also facing threats from other factions in the Highschool DxD universe. This would involve a lot of character development and relationship building within the harem.

One idea could be an OC who is a transfer student with a unique power. The harem could form as different characters in the Highschool DxD world are intrigued by this power and gradually fall for the OC. For example, the OC might have the ability to heal wounds instantly, which is very useful in the battles that often occur in the DxD world.

One idea could be the main character, as the harem queen, having to deal with rivalries among the members of the harem. Maybe there's a new girl who challenges her position and she has to prove herself through various magical trials.