In a Naruto and Highschool of the Dead fanfiction, Rei could have an interesting role. Maybe she could possess some ninja - like skills similar to those in the Naruto universe. For example, she might be able to use chakra in a way that is unique to her character, perhaps using it to enhance her physical abilities during the zombie apocalypse that is central to Highschool of the Dead. This would make her a more formidable fighter and could lead to some really cool action scenes in the fanfiction.
Some Naruto characters would likely be very confident in a Highschool of the Dead - Rei fanfiction setting. For example, Naruto himself would probably jump right into action against the zombies. He'd see it as another challenge to overcome and would use his Rasengan or other jutsus without hesitation. Sasuke, on the other hand, would be more calculating. He'd analyze the situation of the zombie apocalypse and the role of Rei and others before making a move.
One great Takashi x Rei fanfic could be 'A New Beginning'. It shows how Takashi and Rei's relationship evolves in the post - apocalyptic world. They face many challenges together and their bond strengthens through shared experiences.
Another theme is the growth of their relationship. It might start as a simple friendship or a reluctant alliance, but as they face challenges together, it evolves into something deeper. There could be moments of jealousy or misunderstandings as well, which are common in relationships.
A fanfic like this would likely have a very complex plot. The characters from Naruto would bring their own goals and values into the Highschool of the Dead world. Sasuke, for instance, might be more interested in using the chaos to gain power, while Naruto would be focused on saving everyone. And with the Juubi in the mix, there could be a race to either harness its power for good or prevent it from causing even more destruction. It could also explore how the different fighting styles and abilities in Naruto compare to the survival skills needed in a zombie - filled high school.
A more complex fanfiction could be about a joint mission between the two universes. The leaders of both worlds realize that there is a common threat that only the combined forces of Highschool DxD and Naruto can defeat. So, they send their best characters, like Rias and Sasuke, to work together. This would involve a lot of character development as they learn about each other's cultures and powers.
One idea could be a crossover where Naruto characters are transported to the world of The Highschool of DxD. For example, Naruto himself could end up at the high school and his ninja skills would be quite a shock to the devils and other beings there. He might get involved in the Rating Games, using his shadow clones and other jutsu to his advantage.
Perhaps a plot where Takashi and Rei get separated from the rest of the group. They have to find their way back while also dealing with their own feelings for each other. Along the way, they discover new things about themselves and their relationship, like Takashi learning more about Rei's past and why she's so strong - willed.
Naruto's experience in dealing with tough opponents in his own world would help him in the zombie - filled Highschool of the Dead. He would be able to quickly analyze the situation, figure out the weaknesses of the zombies, and come up with effective plans. His friendship - first approach might also lead to some interesting relationships with the other characters in this new and dangerous world.
One idea could be that Naruto, with his godlike powers, somehow ends up in the world of Highschool DxD. He meets Lucifer and they initially have a clash due to misunderstandings. Naruto's power might surprise Lucifer and his followers. As the story progresses, they could find common ground and team up against a greater threat that endangers both Naruto's world and the Highschool DxD universe.
One idea could be that Clem somehow gets transported to the Naruto universe. Maybe she has to learn chakra control and ninjutsu to survive in this new world filled with shinobi. She could form an unlikely alliance with Naruto, given their shared experiences of growing up in tough situations.