One plot idea could be that Naruto, with his ninja skills, gets transferred to the High School DxD world. He might accidentally join the Occult Research Club and use his Rasengan to defend the club from various threats. His positive attitude and never - give - up spirit could inspire the DxD characters and also attract the girls in the harem, leading to some comical and action - packed situations.
Maybe Naruto has a special ability that is misinterpreted in the High School DxD world. For example, his chakra could be seen as a strange demonic power. This causes both confusion and fascination among the characters. As for the harem aspect, the female characters might be drawn to his unique powers and his kind heart. They start to compete for his attention, which creates a fun and flirty dynamic in the fanfic.
One plot idea could be the characters from Naruto finding themselves in the world of High School DxD and having to adapt to the different rules and powers there. They might form alliances with the characters from DxD to face a common enemy.
You could write a fanfic where the two worlds collide due to a powerful magic or jutsu gone wrong. The characters from both Naruto and High School DxD have to team up to fix the problem. This would bring together different personalities and abilities. For instance, Issei's perverted nature could be a source of comedic relief while Naruto's determination could inspire the DxD characters to fight harder.
One plot idea could be that Naruto is summoned to the High School DxD world by a powerful magic user who mistakes him for a powerful demon. Once there, Naruto has to prove that he is not a threat while also trying to find a way back home. Along the way, he befriends some of the students at the school and helps them with their own problems, like protecting the school from a sudden attack by a group of rogue devils.
A plot idea could be that some of the devils in High School DxD want to learn the secrets of chakra from Naruto. So they kidnap him to their world. Naruto then has to find a way to escape while also dealing with the political intrigue among the devils, angels, and fallen angels. Another idea is that Naruto's shadow clones could be mistaken for some new type of summoned creatures in the DxD world.
A possible plot for 'naruto high school harem fanfiction' could be that Naruto is given a special project in high school where he has to work with a group of girls. As they work together, the girls start to develop feelings for Naruto. There could be drama within the group as some girls are more forward in their feelings while others are shy. And Naruto, being his oblivious self at first, slowly starts to realize the situation and has to figure out how to handle all these new emotions and relationships.
Well, perhaps the main character in the 'pokemon high school harem fanfic' is a trainer who has a special pokemon that can transform into different forms. The female characters in the harem are all from different pokemon battling teams. They become interested in the main character because of his unique pokemon and his kind heart. As they interact more in high school battles and training sessions, the harem dynamic develops.
One idea could be a crossover with 'Fate/stay night'. You could have the characters from High School DxD enter the Holy Grail War. Issei could use his boosted gear in new and exciting ways against the Servants. Another idea is a crossover with 'Naruto'. The ninjutsu from Naruto's world would be a cool addition to the battles in High School DxD. For example, Sasuke's Sharingan could create some interesting interactions with the devil eyes in DxD.
You could also base the fanfic on a tournament arc. All the characters from the series participate in a high - stakes tournament with unique rules. This would allow for a lot of action - packed scenes and strategic battles. The main character could face off against some of the toughest opponents and discover new things about their powers along the way.
One idea could be a sports competition at Konoha High School. Naruto could be on the track and field team, trying to break records. Another is a school play where the characters have to act out historical ninja battles in a comical way. Maybe there could also be a mystery involving a stolen scroll from the school's ninja history museum.
One idea could be a school sports competition where Naruto's ninja skills give his team an edge in events like track and field. Another could be a school mystery where Sasuke uses his Sharingan to solve it.