An image processing mechanism of a game apparatus includes a first motion control mechanism and a second motion control mechanism. The first motion control mechanism controls the motion of a first character appearing in a game space in response to an operation performed on a first operation switch included in a plurality of operation switches. The second motion control mechanism controls the motion of a second character also appearing in the game space but different from the first character in response to an operation performed on a second operation switch, and changes the motion of the first character based on the motion of the second character. Thus, the present game apparatus makes a relationship between a player and subjects of operation involved, thereby allowing the player to experience a novel sensation in playing a game.