We propose a system for a media art work named "A soul of a trail", which generates tracinglines vurtually in the air corresponding to motions of a handy input device. When an experience person draws lines in the air with a direction rod, the system extracts a designated color and outputs correspoinding pixels on a CRT monitor. After a short duration, the virtually generated trails begin drifting and transforming on the screen, and then vanishes out. Through the experience with this system, a person can have and realize a feeling that he draws an object in an 3D-space canvas.