Well, a great plot for Kingdom Hearts Aqua crossover fanfiction would be if she crossed over into the Pirates of the Caribbean world. She could encounter Jack Sparrow and his crew. Maybe she has to help them find a special treasure that is actually a key to a new door in the Kingdom Hearts universe. Or she could cross over into the world of Tangled. Rapunzel's long hair could have some sort of magical connection to the power of the Keyblade, and Aqua has to figure out how to use it to defeat an encroaching darkness.
One idea could be Aqua crossing over into a different Disney world, like Wonderland. She could have to navigate the strange rules and characters while still maintaining her Keyblade skills. Another could be a crossover with a Square Enix game universe other than Kingdom Hearts. For example, she might end up in the world of Final Fantasy and team up with some of those characters to face a new threat that somehow links both universes.
A really cool plot could involve Aqua crossing over into a modern - day Earth setting within the fanfiction. She would be out of place, with her Keyblade and her other - worldly appearance. But she discovers that there are remnants of the Heartless on Earth that are causing chaos in a big city. She teams up with a local group of people who have an unusual ability to sense the Heartless, and together they fight to cleanse the city of this darkness.
One idea could be a crossover adventure where Aqua and Erza team up to face a powerful dark force. Maybe they start off as rivals, with Aqua's Keyblade skills and Erza's swordsmanship clashing in a misunderstanding. But as they realize they share a common enemy, they combine their powers. Aqua could use her magic to support Erza's more direct combat approach.
Well, a great plot could be Roxas finding himself in a crossover with a Final Fantasy world. He meets some of the iconic Final Fantasy characters like Cloud or Tifa. They initially suspect him because of his connection to the Heartless and Nobodies. But as they get to know him, they realize he's on their side in the fight against a new enemy that is trying to use the power of both the Kingdom Hearts and Final Fantasy universes. It could be a story full of action, character development, and exploring the differences and similarities between the two universes.
Well, perhaps in this fanfiction, the Organization XIII has a plan to use Elsa's powers for their own evil purposes. They manipulate events in Arendelle to make Elsa feel isolated and out of control. Sora, Donald, and Goofy show up and befriend Elsa, showing her that she can trust others. They then have to battle the Organization XIII members while also dealing with the internal struggles of Arendelle's characters, like Anna's determination to save her sister no matter what.
A possible plot is that the Soul Reapers discover the existence of Kingdom Hearts. They might think it's some sort of powerful spiritual object. Rukia could be the first to encounter a Keyblade wielder like Sora. Sora, in turn, could be intrigued by the Soul Reapers' powers and their way of dealing with the afterlife. The two groups could then join forces to stop a common enemy that threatens both their worlds. Maybe an ancient evil that wants to use the power of Kingdom Hearts and the souls in the Bleach universe for its own dark purposes.
One idea could be a story about Aqua's training in the past. It could explore how she mastered her keyblade skills, the challenges she faced, and the friendships she made during her training days. Another could be a story where Aqua travels to different worlds in the Kingdom Hearts universe in search of something, like a rare magic item that could help her defeat the darkness. And a third idea could be a story that focuses on Aqua's relationship with her friends, like Terra and Ventus, and how they support each other through difficult times.
One idea could be exploring the backstories of the new characters introduced in Kingdom Hearts 3 in more depth. For example, you could write about how they came to be in the different worlds and what their true motives are.
In a crossover fanfiction, Aqua could be paired well with Mickey Mouse. Mickey has a deep understanding of the Kingdom Hearts universe and his magic could complement Aqua's Keyblade abilities. They could embark on a journey together to uncover some ancient secrets that are crucial to both their worlds. Also, Elsa from Frozen could be a great pairing. Elsa's ice powers and her struggle with her own identity could find an interesting parallel with Aqua's journey and her powers. They could help each other grow and face challenges together.
I'm not sure there is an official 'sexy' version of the Kingdom Hearts Aqua story. In the regular Kingdom Hearts, Aqua is a keyblade wielder. She is strong and brave. She embarks on a journey to protect her friends and the worlds from the forces of darkness. She has to face many challenges and enemies along the way.
One idea could be that the Heartless somehow find their way into the Marvel universe and start attacking various locations. The Avengers, being the protectors, team up with Sora and his friends from Kingdom Hearts. They initially have some clashes due to different fighting styles and ways of understanding the world, but eventually learn from each other and combine their powers to defeat the Heartless. For example, Iron Man could use his technology to analyze the Heartless' weaknesses, while Sora uses his Keyblade to directly combat them.
One idea could be that Sora finds himself in a new world where he is surrounded by characters from different Kingdom Hearts realms who all have a strong attraction to him. They compete in a friendly way to go on adventures with him.