The phrase "main character" refers to the most important person in a story, movie, or book. They are the one who the story is mostly about and who goes through the most changes or experiences the biggest events. Full definition
You do meet a lot of main characters from the anime and can have fun customizing your character at will. (amazon.com)
You don't see a lot of children as main characters in videogames, and the game is able to portray the innocence of youth surprisingly well. (thatvideogameblog.com)
Still though as I played I was teased with fighters that I wished were introduced in the game as main characters. (mammothgamers.com)