A formation information storage unit stores formation information regulating a formation which characters should form. A character control unit turns off assessment of contact between allies when the characters are to formate and, based on formation information, assembles the respective characters in respective positions. Then, after the characters are assembled, the character control unit turns contact assessment back on. Further, when the characters are to attack, the character control unit moves front row characters toward enemy characters and makes back row characters follow the front row characters, while maintaining a certain amount of space therebetween. Then, when a front row character is destroyed, a back row character replaces the destroyed character.