Well, one way it could work is if there was some sort of multiverse crossover concept. Maybe in a world where different fictional universes collide. Naruto's skills like his shadow clone jutsu could be used in interesting ways to help Wonder Woman in battles. He could also teach her about the importance of friendship and determination which are big themes in his story.
In this fanfiction idea, Naruto being Wonder Woman's older brother could mean he imparts his ninja way of life to her. For example, he might train her in stealth and agility which could enhance her already amazing combat skills. Also, Naruto's ability to never give up could inspire Wonder Woman during tough times, and they could form a really strong sibling bond that helps them face any threat together.
If we consider a scenario where both are summoned to a world in need of saving. Naruto with his rasengan and shadow clone jutsu, and Wonder Woman with her bracelets and super strength. They would have to rely on each other in battles. The initial attraction could be based on their mutual respect for each other's combat abilities. As they camp together between battles, sharing stories of their home worlds, they would start to understand each other on a deeper level. This understanding could be the foundation for a romantic relationship between the two.
Well, in this fanfiction concept, it could work in terms of Naruto's protective nature. Naruto is known for his loyalty and his will to protect those he cares about. If he were Erza's older brother, he would surely use his skills and abilities to keep her safe. He could teach her some of his ninja techniques, which would be really cool to see combined with Erza's own combat skills. Also, Naruto's positive attitude could influence Erza in a different way, making her more open and perhaps less brooding at times.
The storyline could start with Naruto somehow ending up in Wonder Woman's world. Maybe through a magical portal. Once there, he discovers his connection to Wonder Woman and decides to protect her as an older brother. They would then face various threats together, with Naruto using his ninja skills and Wonder Woman using her superpowers.
Well, one way it could work is through some sort of multiverse concept. Maybe in a particular multiverse, the magical world of Harry Potter and the superhero world of Wonder Woman collide. Harry could have some sort of hidden connection to the Amazonian world. His magic could be related to the powers that Wonder Woman has in a different way. For example, his spell - casting could be a form of magic that was lost in the Amazonian world long ago.
In a Naruto and Wonder Woman romance fanfic, their relationship could be built on mutual respect for each other's cultures. Naruto comes from a world with ninjas, chakra, and unique clans. Wonder Woman hails from Themyscira with its Amazonian culture. They could learn from each other. For example, Naruto could teach Wonder Woman about the importance of teamwork in the ninja way, while she could introduce him to the values of the Amazons. This exchange of ideas and values could lead to a deep emotional connection and eventually a romantic relationship.
It could work if there was a shared backstory created for them. Perhaps they both have a common ancestor or some ancient power that links them. Naruto's strong sense of loyalty and protection could be extended to Natsu as his younger brother. He could teach Natsu some of his ninja values like never giving up and the importance of teamwork. Natsu, in turn, could show Naruto the more carefree and adventurous side of the Fairy Tail world.
They could go on adventures to stop ancient evils that are awakening in both their worlds. For instance, an ancient demon from Naruto's world might be summoned by a villain in the DC universe. Together, they would have to use their combined skills to stop it. Naruto could use his Rasengan while Wonder Woman uses her bracelets to deflect attacks.
The older brother in the fanfiction might be a character with a tragic past. For example, he could have been experimented on by Orochimaru and gained some strange powers as a result. And he returns to the village later to protect Naruto from the threats that are coming towards him.
Well, in a fanfic, anything can be possible. Maybe in an alternate universe where the DC and Naruto universes collide. Naruto's ninja skills could be combined with Wonder Woman's superpowers in some unique ways. For example, Naruto's shadow clone jutsu could be used in combat along with Wonder Woman's lasso of truth. They could fight against common enemies that threaten both their worlds.
In fanfiction, the idea of Harry being Naruto's older brother might be possible if we consider that both characters have some similarities in their personalities. They are both determined and face great challenges. So, a writer could create a backstory where there is some sort of connection between their two worlds that makes them family. For example, perhaps a wizard from the Harry Potter world visited the Naruto world long ago and had a relationship that led to Harry and Naruto being related.