At first, Naruto might see Ophis as a powerful ally he needs to understand in order to protect his world. He would try to approach her with respect. Ophis, seeing Naruto's pure heart, would allow him closer. They would then go through various challenges together, like facing enemies that threaten both their existences. During these trials, they would rely on each other, and Naruto's positive attitude would start to melt Ophis' cold exterior. Their bond would strengthen over time until they realize they can't live without each other and decide to get married.
The exploration of different worlds or dimensions is also a theme. Since Ophis has connections to different realms, fanfictions often take Naruto and Ophis on adventures through these strange and new places. This allows for a lot of creativity in terms of world - building and the discovery of new and unique things.
In a Highschool DxD - Naruto crossover fanfiction with Ophis, she could form an alliance with some of the Akatsuki members. They might be interested in her power and knowledge. Ophis could use this opportunity to learn about the unique chakra system in Naruto. This could lead to a series of battles and power - up scenarios as she tries to adapt to this new world and the Akatsuki tries to use her for their own goals.
In this fanfiction, perhaps Naruto is transported to a dimension where Ophis is a powerful figure. Naruto, with his strong sense of justice, tries to understand Ophis' motives. He may initially be in awe of her power but then realizes that there are some dark aspects to her actions. He then has to decide whether to side with her or oppose her while also trying to find a way back to his own world.
One main theme is power. Naruto already has his own set of powers, and when combined with Ophis' abilities, the exploration of new power levels and how to control them is a big part. For example, in some fics, Naruto might struggle to master a power given by Ophis.
Well, it could be that Fem Naruto, with the power or characteristics of Ophis, has to face the challenges in the Naruto universe in a different way. Maybe she uses Ophis - like powers to defeat stronger enemies or to gain respect in the village that once shunned Naruto.
Obviously Naruto and Ophis. Naruto is the main protagonist from the Naruto series, and Ophis is from another fictional context. There could also be some of Naruto's friends like Sasuke or Sakura who might be involved in some way. Maybe they are worried about Naruto when he disappears into Ophis' world.
One possible plot could be that Naruto, with his determination and strong will, somehow meets Ophis in a different dimension or realm. Ophis, being a powerful being, is initially intrigued by Naruto's unique chakra. Naruto, in turn, is drawn to Ophis' mystery. They start to understand each other's worlds and gradually fall in love. Eventually, they decide to get married, uniting their different powers and cultures in a way that brings peace and new possibilities to both their realms.
In a more comical plot, Ophis could be shrunk down to a more human - like size and lost in the Hidden Leaf Village. Naruto finds her and mistakes her for a lost child at first. As he tries to help her, she gets frustrated with his naivete but also finds it endearing. Over time, their relationship evolves into a romantic one, and the kiss is a sweet moment that surprises all the villagers who have been watching their strange relationship develop.
I'm not entirely sure as it's a fanfiction, but Ophis is likely a unique character created for this particular story. Maybe she's a powerful witch or some sort of magical being.