Well, I've come across some interesting ones. Some fanfics blend the magic systems really well. For example, they might have Harry learning about the power of the Keyblade while still using his wizardry skills. However, the quality can vary a lot. It's important to read reviews or summaries first to find the ones that suit your taste. You could also check out fanfiction forums where people discuss and recommend their favorite crossovers between these two universes.
Some Kingdom Hearts 3 crossover fanfictions cross over with the Pokémon universe. Imagine Sora traveling to the Pokémon world, where he has to catch Pokémon instead of using the Keyblade all the time. He could form a team of Pokémon and use them in battles against Heartless that have invaded the Pokémon world. The concept of friendship and growing stronger with your companions, which is central to both Kingdom Hearts and Pokémon, is emphasized in these crossovers.
Character interaction is a key element. Axel interacting with characters from different universes can lead to interesting dynamics. For example, his fiery personality might clash or blend well with more reserved characters.
Yes, there are quite a few out there. Some fanfictions might explore how the characters from Kingdom Hearts would interact with those from Harry Potter. For example, Sora could end up at Hogwarts and have to deal with the magic there while also trying to find his friends. It's a really cool concept that combines the unique magic systems of both universes.
One interesting plot could be that the ponies from MLP accidentally find themselves in the Kingdom Hearts universe. They might mistake the Heartless for some kind of dark magic creatures from their own world and try to fight them using their magic. For example, Twilight Sparkle could use her powerful spells to combat the Heartless while trying to figure out how to get back to Equestria.
The Keyblade wielders like Sora, Riku, and Kairi would bring a sense of adventure and a different kind of magic to Equestria. The ponies, on the other hand, could teach them about the power of friendship in a more direct way. Donald and Goofy might be a bit startled by the ponies at first but would soon get used to them. Donald's magic could be compared to the magic of some of the unicorn ponies, and they could exchange magical knowledge.
One interesting storyline could be Sora and the gang from Kingdom Hearts getting lost in the world of DuckTales. They could team up with Scrooge McDuck to search for a special keyblade that's hidden in one of Scrooge's many treasures. This would bring together the magic of Kingdom Hearts and the adventure - seeking nature of DuckTales.
One possible plot could be that Sora and his friends land in the underwater world of The Little Mermaid. Ariel could be in trouble, perhaps captured by the Heartless. Sora, with his Keyblade, would fight to free her. Donald and Goofy could help by using their magic and strength respectively. They would then have to find a way to restore the underwater kingdom's heart which has been affected by the Heartless presence.
One possible plot could be that Naruto and his friends are somehow transported into the Kingdom Hearts universe. Naruto, with his never - give - up attitude, could team up with Sora to fight against the Heartless. They might learn new techniques from each other. Naruto could teach Sora some of his ninja skills like shadow clone jutsu, and Sora could show Naruto how to use the Keyblade more effectively in combat.
One possible plot could be that Sora from Kingdom Hearts accidentally ends up in the Bleach universe. He teams up with Ichigo to fight against a new threat that is causing chaos in both their worlds. They have to combine their unique powers, like Sora's Keyblade skills and Ichigo's Soul Reaper abilities, to defeat the enemy.