When someone joins your game, they take control of any of the other 3 main characters. When they spend level-up points, or earn gear, that gear is saved and those level up points are saved but they do not take those levels or gear back to their own game. It stays on yours. If they join you again they will pick up where they left off with that character, and will of course automatically level up to match your main character's level if it hasn't done so already. and they will also have the same equipment they left the character with.
What I -DONT- know is if, lets say they are playing katarina and you gain 5 levels without your friend but have the AI play katarina. If you give her new equipment, I don't know if they get to use that equip or if it rolls her equipment back to what she had when you two last played together.
basically, any progress made will only be while they play on your game. Won't go back with them to their own game. You play co-op to help a friend and/or you play together only. :3
GT: Ezmarii/CapitalStorm91
rent my dragons dogma pawns! :)