One idea could be that the human girl is a scientist who accidentally stumbles upon Loki while he's on a secret mission on Earth. She initially fears him but then realizes he's not all bad and they end up teaming up to solve a mystery that threatens both Asgard and Earth.
For Loki, start with his known traits like his mischievousness and arrogance. As he interacts with the human girl, show how her humanity softens him. For example, her kindness might make him question his motives. For the girl, if she's initially shy, show how Loki's boldness draws her out of her shell.
One popular theme is Loki's struggle with his identity as a human. Since he's used to being a god, becoming human can be a big adjustment, and many fanfictions explore this aspect.
One idea could be Loki and Hulk teaming up to take on a common enemy. Maybe a powerful sorcerer who is threatening Asgard and Earth alike. Loki uses his cunning and magic, while Hulk provides the brute strength. Another could be a story where Loki tries to trick Hulk for his own gain but ends up learning a valuable lesson about friendship when Hulk shows unexpected kindness.
A unique Loki Marvel fanfiction idea could be Loki getting trapped in a time loop. Every day he has to relive the same events but tries to find a way to break the loop and change his fate. Or perhaps a story where Loki has to pretend to be another popular Marvel hero and hilarity ensues as he tries to act like them. Another concept is Loki forming an alliance with the villains of the Marvel universe but with his own hidden motives.
Loki could be injured while exploring a dangerous new realm. He's attacked by strange creatures and sustains a life - threatening injury. His journey to recover could involve him having to rely on a local healer who has a very different view of magic from his own. This forces him to adapt and learn new ways to heal.
Imagine a Loki OC who is a half - Asgardian, half - Vanir orphan. This OC has been living on the fringes of society, but Loki discovers their existence and decides to use them for his own schemes at first. However, the OC's pure heart and kind nature start to change Loki's perspective, and they end up on an adventure together to uncover a long - lost secret about their shared heritage.
One idea could be that the vampire girl is initially drawn to the human boy because of his pure heart. She tries to protect him from other vampires who see him as easy prey. For example, she uses her super speed and strength to fend off attacks.
One idea could be that Loki and Tony are both tributes in the Hunger Games. Loki uses his magic to create illusions and mislead other tributes, while Tony uses his tech - savvy mind to build improvised weapons from the resources in the arena. Their different skills and personalities would lead to some interesting interactions as they try to survive and maybe even outwit the Capitol.
Another idea could be 'loki x a magical being from another realm'. This would open up a world of possibilities for adventures, magic - based storylines, and a unique relationship. It could involve exploring different cultures and magics in the fictional universe.
Well, a plot could involve Loki and Jane being accidentally transported to a parallel universe where their roles are reversed. Jane has to deal with the politics of Asgard while Loki tries to understand Earth's scientific concepts. Or, perhaps they are both caught in a time - loop where they keep repeating a day, and they have to figure out how to break it together, learning more about each other in the process.