Overall, the Little Witch Academia series adheres closely to the manga. Some small tweaks might be made for better visual presentation or narrative flow, but the core elements remain intact.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). There are often tags and filters that can help you narrow down to the specific crossovers between My Hero Academia and Little Witch Academia. Many authors post their creative works there, and you can find a wide variety of stories, from action - packed adventures to heart - warming friendships.
First, know the characters well from both series. Understand their personalities, powers, and backstories. This will help you create believable interactions in your fanfiction. For example, if you're writing about Izuku Midoriya from My Hero Academia meeting Akko from Little Witch Academia, you need to think about how their different outlooks on heroism or magic would play out.
One idea could be a crossover where the students from Little Witch Academia visit UA High. They could participate in a joint training exercise. The witches could use their magic in creative ways during combat scenarios, while the heroes-in-training show off their quirks. It would be a fun mix of different powers and personalities.
One great aspect of 'little witch academia crossover fanfiction' is the potential for unique character interactions. For example, when characters from 'little witch academia' are crossed over with characters from another magical - themed series, it can create really interesting storylines. Maybe a character from 'little witch academia' could learn a new spell from a character in the other series, which would add an exciting new element to the story.
One really good 'little witch academia crossover fanfiction' is the one where it crosses over with 'Harry Potter'. It combines the magical school elements in a really interesting way. You can find it on many fanfiction websites.