A server includes a storage unit storing characteristic data objects of each user, each characteristic data object having a first parameter value representing an ability of the characteristic data object to exert power, a second parameter value representing an ability to reduce the first parameter value of each characteristic data object of another user different from the user having the characteristic data object, and one of attributes having a superiority-inferiority relationship relative to each other. The server further includes a receiving unit receiving a game proceeding instruction from a device of each user, and a parameter adjusting unit adjusting the second parameter value of each characteristic data object of the user of the device, based on a first number of characteristic data objects of the user that have an attribute superior to a first attribute assigned among characteristic data objects of a second user different from the user.