An image processing apparatus includes circuitry to authenticate a first user, a display to display an initial screen to the first user, after the first user is authenticated, and a communication device to wirelessly communicate with a portable terminal device operated by the first user to control a display of the portable terminal device to display an additional initial screen based on display contents of the initial screen. The circuitry further determines whether at least one of the image processing apparatus and the portable terminal device is not in use. Based on a determination indicating that the at least one of the image processing apparatus and the portable terminal device is not in use, the circuitry determines whether any user is present at the image processing apparatus, using a detector that detects human presence at the image processing apparatus to generate a first determination result.