Player Square (プレイヤースクエア Pureiyā Sukuea) is the Square where Player Card and Start Card are placed at the start of the game. Player Square are represented by the square with icon on the right diagram. It is the middle Square in Army Area.
Each player has their own Player Square. You cannot put your own Z/X into your opponent's Player Square and vice versa. Unlike Normal Square, Player Square can be attacked regardless of the presence of any Z/X in there. If an empty Player Square (Player Square without any Z/X on it) is attacked, the player in the possession of that Square takes 1 damage. Because of this, Player Square is essentially the main target of assault during the game.
Unlike other Square, there is only a small amount of card abilities and effect that able to affect the Player Square. Most of them only affect your Player Square, either by giving the Z/X on it some kind of support or protection from attack. But some, like Void Bringer, is able to affect the opposing Player Square as well.