Well, one possible plot could be that Supergirl accidentally lands in the Naruto universe. Naruto, being the curious and friendly ninja he is, approaches her. They initially have a misunderstanding due to their different worlds and powers, but then they realize they can learn from each other. Supergirl could teach Naruto about her advanced technology from her world, while Naruto could show Supergirl the unique chakra - based powers and the ninja way of life.
Maybe in the 'naruto supergirl crossover fanfiction', there is a common enemy. A powerful being from another dimension is threatening both the Naruto world and Supergirl's world. So they team up. Supergirl uses her super strength, flight, and heat vision, while Naruto uses his Rasengan and Sage Mode. Along the way, they also meet other characters from both universes who either help or hinder their mission.
A really interesting plot could be a time - traveling crossover. Supergirl goes back in time to the era of the original Avengers. She helps them in a battle that changes the course of history. In return, the Avengers help her find a way back to her own universe. During this time, she forms a special bond with Thor, as they both have superhuman strength and a connection to otherworldly powers.
Well, it could be that Supergirl lands in the wizarding world somehow. Maybe she's chasing a bad guy who uses magic to escape to Hogwarts. And then she teams up with Harry Potter to fight the bad guy. Harry could teach her about magic while she teaches him about her superpowers.
One possible plot could be that the Supergirl characters find themselves in the world of Glee. Maybe Kara has to blend in at McKinley High while also dealing with her superpowers. She could join the glee club and use her super - hearing to help them perfect their harmonies. And she might have to face off against some villains who are after her while trying not to expose her true identity to her new friends in the glee club.
Perhaps in this fanfiction, Supergirl is accidentally sent to Lucifer's world. Lucifer, intrigued by her powers and pure heart, decides to help her get back to her own world. Along the way, they face various threats together and learn from each other's moral compasses.
Well, one possible plot could be that Supergirl is somehow transported to the Young Justice universe. Maybe there's a dimensional rift caused by some villain's experiment. She then teams up with the Young Justice team to stop this villain from causing more chaos across different dimensions. They could learn from each other's skills and powers along the way.
One possible plot could be that Supergirl, through some sort of inter - dimensional rift, ends up in the Star Wars universe. She might team up with the Rebel Alliance. Her superpowers would be a great asset against the Empire. For example, she could easily take down Imperial starships with her heat vision or super strength. Maybe she'd have to learn to use a lightsaber too, which would be an interesting addition to her powerset.
In this fanfiction plot, Naruto and Supergirl could meet during a crisis situation. Let's say an interdimensional rift has opened and is causing chaos in Supergirl's city. Naruto, being used to strange situations, jumps right into action. Supergirl is impressed by his courage. Together, they could combine their abilities in unique ways. Naruto's Rasengan could be enhanced by Supergirl's super strength when she throws him towards the enemy. And Supergirl could learn some stealth and evasion techniques from Naruto.
It could be an evil ninja from Naruto's world who somehow gains Kryptonian - like powers. He becomes power - hungry and decides to take over both the Naruto world and Supergirl's world. His knowledge of ninja techniques combined with super strength and other abilities would make him a formidable foe.
The fanfiction could start with Supergirl sensing an unusual energy signature, which turns out to be Naruto arriving in her universe. Naruto, being godlike, has an air of mystery around him. At first, Supergirl is cautious. However, as they interact, they find that they share a sense of justice. They could team up to protect the innocent in Supergirl's city. Naruto's skills in stealth and reconnaissance, combined with Supergirl's super senses, make them an unbeatable duo in preventing crimes. As the story progresses, they might face challenges from those who fear Naruto's power or are jealous of Supergirl's popularity. But through it all, their bond grows stronger.
One possible plot could be that Naruto, through some sort of multiverse portal, ends up in Supergirl's world. He brings his unique ninja skills and charisma. The harem aspect could involve several female characters from both Naruto's and Supergirl's universes being attracted to him. For example, Sakura from Naruto's world might follow him through the portal, and in Supergirl's world, characters like Lois Lane could also be drawn to his mysterious abilities and kind heart.