The protagonist of each game is designed by the player. The default name for the PC in Horse Hall is Mary Sue and she is a wildseed freshman from New Hampshire. Being a wildseed she's fairly ignorant about most magical traditions and how the magical community deals with things, especially pertaining to people like her. She's apparently very knowledgeable about the non-magical world however, like knowing when the Canadian Thanksgiving happens even though she's American. She is good at running and likes sports but does not like to sing in public. The PC is a very inquisitve character, always asking questions about things she's never heard of, especially when it has something to do with the magical world, but whether or not she's going to be considered strange and/or cute by other characters depends on the player and what choices they make in-game.
Along with the students there are also teachers.
It can be assumed that there are other teachers and staff in the academy but they have not been named or appeared on-screen.
The PC's family is never shown but they sometimes send letters. The only family shown in-game are Virginia's brothers who go to the academy, Ellen's parents who figure prominently in her storyline are never shown in-game, and for that matter neither does Virginia's. No townspeople are ever shown, only magical characters.