This paper proposes new method for object reference which enables a person to find surrounding objects and develops a navigation system named CoCo. CoCo employs an ultrasonic directional speaker with a rotating base. Ultrasonic wave transmitted by an ultrasonic directional speaker is converted to audible sound when it reflects on floor, wall, or object. Based on this property, CoCo can emit audible sound from arbitrary place using a rotating base. When CoCo navigates a person to an object, CoCo transmits ultrasonic wave so as to hear audible sound continuously from the line between the ultrasonic directional speaker and the object. We designed and implemented an object management system as an application using 3D position sensors and a navigation system CoCo. This paper shows how CoCo navigates a person to an object using position data from an object management system.