An image processing apparatus, comprising: a login/logout control unit configured to control login and logout processes in response to login and logout requests; a user interface unit configured to receive an operation event indicating a function request to use an image processing function or a login request, wherein the user interface includes a display screen and receives an operation event indicating a login request generated when a user selects a login button and an operation event indicating a function request generated when the user selects a function button; a login processing unit configured to, if the operation event indicates a login request: - request user authentication based on authentication information of a user, - generate login information, the login information including a user identifier and access right information of the user, and a guest login processing unit configured to, if the operation event indicates a function request: - obtain guest login information including a guest user identifier and access right information of a guest user from a storing unit of the image processing apparatus, wherein the access right information indicates a right to access an image processing function, an access control unit configured to disable access control on the image processing function based on the access right information in the login information if the operation event indicates a login request or the guest login information if the operation event indicates a function request; and a usage history recording unit configured to record a usage history of the image processing function in association with the guest user identifier in the guest login information if the operation event indicates a function request or the user identifier in the login information if the operation event indicates a login request. a login/logout control unit configured to control login and logout processes in response to login and logout requests; a user interface unit configured to receive an operation event indicating a function request to use an image processing function or a login request, wherein the user interface includes a display screen and receives an operation event indicating a login request generated when a user selects a login button and an operation event indicating a function request generated when the user selects a function button; a login processing unit configured to, if the operation event indicates a login request: - request user authentication based on authentication information of a user, - generate login information, the login information including a user identifier and access right information of the user, and - request user authentication based on authentication information of a user, - generate login information, the login information including a user identifier and access right information of the user, and a guest login processing unit configured to, if the operation event indicates a function request: - obtain guest login information including a guest user identifier and access right information of a guest user from a storing unit of the image processing apparatus, wherein the access right information indicates a right to access an image processing function, - obtain guest login information including a guest user identifier and access right information of a guest user from a storing unit of the image processing apparatus, wherein the access right information indicates a right to access an image processing function, an access control unit configured to disable access control on the image processing function based on the access right information in the login information if the operation event indicates a login request or the guest login information if the operation event indicates a function request; and a usage history recording unit configured to record a usage history of the image processing function in association with the guest user identifier in the guest login information if the operation event indicates a function request or the user identifier in the login information if the operation event indicates a login request.