Abstract: A computer system and a related method are provided to let game systems interact with a trading platform to trade an item such as a virtual good. A game system initiates an inter-system account transfer of a tradable item from a user account of the game system to a first user account of the trading platform. There are further an intra-system account transfer from the first to a second user account, and an inter-system account transfer from the second user account to the user account of the game system. In response to user data relating to the user account of the game system, an access token is returned that is assigned to the first or second user account that corresponds to the user account of the game system. A request is sent to access services to perform the account transfers. The request comprises the access token assigned to the user account.