Perhaps the main character is a boy named Sam. Sam is a bit of a troublemaker usually, but being home alone changes him. He realizes the importance of responsibility. He has to take care of his pet dog while his parents are away. And when some unexpected events happen, like a small fire in the kitchen because he tried to cook something fancy, he learns from his mistakes and becomes more mature in the process of dealing with these situations.
The main character could be a mischievous little boy. He's always getting into small troubles around the house when his family is there. So when he's home alone, he really has a field day. He might try to build a huge fort in the living room or attempt to cook something really elaborate but ends up making a big mess.
The boy might have to fend for himself when his parents go on an unexpected trip. He could face challenges like cooking for himself, dealing with possible burglars, and getting over his fear of being alone at night.
The main character might be a teenager who decides to leave home to join a volunteer program overseas. He wants to make a difference in the world and sees this as his chance to grow and learn outside of his family's protection.
The main villain could be an escaped criminal who stumbles upon the house thinking it would be a good place to hide. But when he realizes there's a kid alone, he decides to take advantage and ransack the place. The kid has to use his wits and the resources around the house to defeat this dangerous villain.
Since we don't have more details about the story, it could be any young man or boy. It might be a character named Tom or Jack, just a normal boy who decides to leave home for one reason or another.
It could be a rogue wizard who has a vendetta against the Dursleys for some reason and decides to attack when Harry is home alone. Maybe the Dursleys once unknowingly wronged this wizard's family, and he wants revenge.
It could be a young lesbian just coming to terms with her sexuality. She might have been struggling in a conservative family or school environment where she felt like an outcast, but then she found a mentor or an older lesbian who guided her and made her feel that she was not alone.
It could be a young adventurer who decides to explore an abandoned house at night.
The main character is the girl who walks home alone at night, though without more context about the specific novel, I can't give more details about her.
Since I don't know the exact 'home alone novel', I can't say for sure. But it could be a young boy or girl as the main character, perhaps with some neighbors or family friends who play important roles.