One possible storyline could be that Queen Lemon is a lost princess from a hidden land in the Naruto world and she ends up in the High School DxD universe. There, she has to find her way back home with the help of the characters from both series. For instance, Issei from High School DxD could use his unique powers to protect her while Naruto teaches her some ninja skills for self - defense.
Another storyline could be that Queen Lemon is a powerful sorceress who can travel between the Naruto and High School DxD worlds at will. She decides to bring some of the Naruto characters to the High School DxD world to help solve a big problem there, like a looming war between the different factions. This would lead to some really interesting cultural exchanges and power - based collaborations between the two groups of characters.
Well, in such a fanfic, it might involve a plot where Queen Lemon is a key to resolving a conflict between the two worlds. The characters from Naruto, like Naruto himself or Sasuke, could interact with the characters from High School DxD. They would have to deal with cultural differences. Naruto's positive attitude might influence the more complex characters in High School DxD, and Queen Lemon could be the catalyst for this interaction.
One interesting storyline could be about the characters' unique power development within the fanfic's universe. For example, a character might gain new powers related to their'slave' status that gives them an edge in battles or challenges. Another could be a story of friendship and loyalty that develops between the main characters despite the complex'slave' relationships depicted in the fanfic.
One possible storyline could be that Naruto, with his unique skills and positive attitude, enrolls in the high school from High School DxD. He might form an unlikely friendship with some of the characters there, like Issei. Together, they could face off against common enemies, with Naruto teaching Issei some of his ninja techniques, adding a new dimension to the battles in the High School DxD universe.
There are also fanfics that might introduce new magical elements or abilities to the characters. Maybe a fanfic where Rias discovers a new power within herself and has to learn to control it, all while dealing with the regular chaos in the school and the underworld.
A good Naruto and High School DxD fanfic would first have well - written characters. The author needs to understand the personalities of the characters from both series and make them act in a way that is true to their original selves. Also, an interesting plot is crucial. It could be something like a common threat that forces the characters from both universes to work together. For example, a new powerful enemy that neither Naruto's ninja skills nor High School DxD's magic can easily defeat.
Power dynamics play a big role too. Naruto is a very powerful ninja, and in the High School DxD universe which is filled with powerful devils, angels, and other supernatural beings, how his power compares and how he uses it is a major aspect. He might have to learn new ways to use his chakra in a world where magic and sacred gears exist.
He could be a new type of threat or ally in the DxD world. Since Naruto has such powerful abilities, the fallen angels might see him as a potential weapon or a hindrance to their plans.
One idea could be to create a fanfic where Naruto is somehow transported to the world of High School DxD. He could bring his unique ninja skills and chakra system. Maybe he teams up with Issei to fight against a common enemy. For example, a powerful devil or fallen angel that threatens both the ninja world and the DxD universe.
One possible plotline could be that a character from Harry Potter accidentally ends up in the world of High School DxD. For example, Ron could be transported there and have to figure out how to get back while dealing with the devils and angels in that world.
There could be a really interesting fanfiction where the Queen of Blades from StarCraft gets inserted into the High School DxD universe. Maybe she could be a powerful new character in the school, causing all sorts of chaos or perhaps she teams up with the main characters to fight against a common enemy. It all depends on the creativity of the writer.