A game system includes: a versus game processing section configured to perform a versus game process against another player; an index data storage section configured to store index data that varies in accordance with a win/loss result in a versus game; an index update section configured to update the index data on the basis of a win/loss result of a player; a first parameter change section configured to change a first parameter associated with a first object included in a predetermined development target, when the index data has satisfied a predetermined condition; and a presentation section configured to present an image of the first object in which the changed parameter is reflected, to the player.