Incorporate some mystery elements. Maybe there's a strange force at work in the combined world of Natsu and High School DxD that is causing chaos. Natsu and the main characters from High School DxD have to work together to figure out what it is. This will make the readers curious and keep them engaged throughout the story.
Natsu, being a fiery and passionate character, would likely have a rather intense interaction with the DxD Highschool characters. He might be initially distrustful due to his recent betrayal. But some of the more friendly characters in DxD, like Issei's group, could try to befriend him. Natsu would probably show off his powers a bit, which would either impress or intimidate the others. And there could be some clashes in personalities, for example, Natsu's straightforwardness against some of the more devious DxD characters.
I'm sorry, but I can't recommend lemon (adult - themed) fanfiction as it goes against ethical and often site - use policies. However, you can try looking for regular Natsu x Highschool DxD fanfiction on popular fanfiction platforms like Fanfiction.net or Archive of Our Own. There you might find some well - written stories about the crossover that are suitable for all audiences.
First, combine the unique elements of both worlds. For example, the technology from Generator Rex and the supernatural aspects of Highschool DxD. You could have Rex's nanites interact with the devil powers in DxD. Maybe a character from DxD gets infected with the nanites and gains new abilities. This creates an interesting conflict and opportunity for character development.
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.
One idea could be a crossover where Natsu finds himself in the world of High School DxD and has to deal with the devils and angels there. He might use his fire magic in unique ways to combat the various threats in that universe.
First, come up with a really unique and interesting monster concept for your OC. For example, a monster that can control time or has the ability to merge with shadows. Then, think about how this OC will interact with the existing characters in Highschool DxD. Maybe they'll start off as an enemy to Issei but later become an ally. Also, create some exciting plot twists. Like, the OC might turn out to be related to one of the powerful beings in the series in a way no one expected.
To create engaging characters, you can start by combining the traits of characters from both series. For example, take the boldness of a Highschool DxD character and mix it with the magical finesse of a Trinity Seven character. This creates a unique blend that readers will find interesting.
One important aspect is to focus on the character development. In Naruto, he has grown from an outcast to a hero. In a crossover fanfiction, you could show how he adapts to the new environment of Highschool DxD. Maybe he starts off being distrusted by the devils and angels because of his unknown power source (the Kyuubi). Then, as he shows his true nature, they start to accept him. Another point is the plot. You could create a conflict that involves both the threats from the Naruto world (like rogue ninja or Akatsuki members) coming into the Highschool DxD world and the internal conflicts within the Highschool DxD world itself, such as power struggles between the different factions. This would keep the story exciting and full of action.
First, you need to research the Highschool DxD universe thoroughly. Understand the rules, the characters, and the overall tone. For the Jesus OC, think about how this character would interact with the existing cast. Maybe your Jesus OC could have special powers related to his divine nature in the context of the Highschool DxD world, like the ability to heal or perform miracles in a unique way. Then, build a plot around the conflicts and relationships that would arise from this new character's introduction. For example, how would the devils, angels, and fallen angels react to this Jesus OC? This could lead to all kinds of interesting storylines.
First, you need to understand the basic elements of both Highschool DxD and the Saiyan concept. Incorporate the Saiyan's power and battle - thirsty nature into the Highschool DxD world. Maybe your OC Saiyan could be a transfer student who surprises everyone with their superhuman strength. Then, think about the relationships they will form. Will they be friends or rivals with the existing characters? Also, consider adding some unique Saiyan - related plot twists, like a special transformation that is triggered by a certain event in the Highschool DxD universe.