Disclosed herein are a method for controlling a server device, a server device, a computer-readable recording medium, and a game system. 
Recently games that are provided from a server device via a communication network to mobile terminals that players are operating have become a hit, and a lot of game titles have been released from a plurality of platforms.  There are a wide variety of types and categories of these games, among which social games allowing a plurality of players to participate in the same game are particularly enjoying a boom.  Such a social game can be said to use a community-forming network service called a social networking service (SNS). 
A known social games utilizing the features of a SNS is configured to let characters (player characters) manipulated by a plurality of players attack one or a plurality of enemy characters to develop a fighting event such as a battle (combat).  In this case, each player becomes a member of a specific group such as a guild, a party, a team or a community, which will be described later, to beat an enemy character, whereby various rewards such as a point or an item that can be used in the game can be given not only the individual players but also to groups to which the players belong. 
Such a fighting event to beat an enemy character by a plurality of player characters is conventionally called a “raid battle” in the field of social games.  In such a fighting event, a group or a guild is represented with its first letter (G), and an enemy character in a raid battle as a raid character is represented with its first letter (R).  Then, such a fighting event is sometimes called a “GvR” (v denotes versus, the same applies in the following). 
Another social game that is widely known offers an individual fighting event that is a one for one fighting of player characters and a group fighting event that is a battle between groups (including not only battles but also competitions such as a team sport).  As one example of the latter, JP2013-66524A describes an online game, in which when matching of a plurality of parties, to which player characters belong, is established in a coliseum hall as a predetermined virtual space in the game, a group fighting (battle) between the parties is performed.  Such a direct fighting between groups is conventionally called a “guild battle” in the field of social games, or may be called “GvG” represented with the first letters (G) of the group or the guild as stated above.