Strengthening a relation between "products" and a virtual space, and improving values of both game characters and the "products" mimicking the characters by stimulating users' affection to original products. In an online game method, a product carrying an ID code assigned thereto and a number of image characters reflecting features of the product and correlated to the ID code are previously prepared, and a user can use the image characters as characters for the online game by inputting the ID code in the online game to register the image characters therein.