Hermione could be a great character to focus on. She is known for her thirst for knowledge. In a 'Harry Potter meets Shadow the Hedgehog' fanfiction, she would be eager to learn about Shadow's world. She might study the science and technology behind Shadow's abilities, trying to find connections to magic. At the same time, she could use her vast knowledge of magic to help Shadow understand the wizarding world better, and she would be a key figure in any alliance formed between the two worlds.
Shadow the Hedgehog could be the most interesting. Imagine his perspective when he enters the wizarding world. He's used to a world of speed and combat, but now he has to deal with magic, spells, and Hogwarts' complex rules. His no - nonsense attitude would clash with the more traditional ways of the wizarding world, and it would be fascinating to see how he adapts and uses his skills to help or cause chaos.
I think Harry Potter himself would be very interesting. He has a whole new world to discover in the world of Shadow the Hedgehog. His reactions to the high - speed action, different technology, and the new types of enemies would be really cool to explore. Also, his magic would be a unique element in that world.