They could have a mentor - mentee relationship. Gabriel, being more familiar with the Highschool DxD world, could guide Harry. For example, teach him about the different factions like the devils, angels, and fallen angels.
A friendship is very likely. They might bond over shared interests such as a love for adventure or a desire to protect the innocent. They could support each other in various school events or battles. For instance, in a school tournament, they could be each other's cheerleaders and also strategic partners.
Well, the plot could involve Harry being a new transfer student to the Highschool DxD world and Gabriel being one of the first to befriend him. Maybe they team up to face some of the common threats in that universe, like the devils or fallen angels. They could also explore their own unique powers together and learn from each other.
She could have her classic Harry Potter abilities like magic. So, she could cast spells, use charms, and perform transfigurations. In the context of Highschool DxD, she might be able to combine her magic with the supernatural elements of that world. For example, she could use magic to enhance her physical abilities like speed or strength, similar to how the devils and angels have their own powers.
One possible plot could be that Naruto is somehow transported to the Highschool DxD universe and meets Gabriel. They might team up to face a common threat that is endangering both the ninja world and the supernatural world of Highschool DxD. Naruto's unique skills as a ninja could be combined with Gabriel's angelic powers in an epic battle against evil forces.
One possible fanfiction could be about a crossover where the characters from Highschool DxD and Naruto are transported to a world where they meet Gabriel. Maybe they team up to fight a common enemy. For example, the devils from Highschool DxD and the ninjas from Naruto could combine their powers under Gabriel's guidance to defeat an ancient evil that threatens all three of their realms.
Devil Naruto might possess the power of flight, which is common among devils in Highschool DxD. His chakra could be infused with devil energy, making his jutsus more powerful and having additional effects like draining the opponent's energy. His shadow clones could also be enhanced to have some devil - like characteristics, such as being able to resist certain types of attacks better.
He could still have his chakra - based powers. His Rasengan, for example, would be a powerful attack. And with his heightened senses, he might be able to detect and counter attacks more quickly. He could also develop new techniques that rely on his other senses, like a sound - based jutsu that can stun opponents.
One popular storyline could be Gabriel's interaction with the main characters from Highschool DxD in a more peaceful school setting. For example, she might be involved in a friendly competition among the different factions at the school. Another could be a story where Gabriel has to adapt to the modern human world while still maintaining her angelic duties. She could face challenges like understanding modern technology or human emotions.
You can try fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Highschool DxD Issei x Gabriel' on their search bars, and you should be able to find relevant fanfictions.
Another way her character develops is through her own self - discovery. Fanfictions often explore Gabriel's identity as an angel in a new light. She might question some of the strict rules and dogmas of the angelic realm. This internal struggle can lead to her evolving into a more complex and independent character. She may start to make decisions based on her own beliefs and values rather than just following what she was taught as an angel, which is a significant step in her character development.
One interesting crossover could be a story where the power - up systems from Highschool DxD and Naruto are combined. For example, the devils in Highschool DxD could learn chakra control from Naruto characters. As for Gabriel, she could be a mediator between the two very different universes. Maybe she uses her angelic powers to help the characters understand each other's worlds.