We propose IM6D, a novel real-time magnetic motion-tracking system using multiple identifiable, tiny, lightweight, wireless and occlusion-free markers. It provides reasonable accuracy and update rates and an appropriate working space for dexterous 3D interaction. Our system follows a novel electromagnetic induction principle to externally excite wireless LC coils and uses an externally located pickup coil array to track each of the LC coils with 5-DOF. We apply this principle to design a practical motion-tracking system using multiple markers with 6-DOF and to achieve reliable tracking with reasonable speed. We also solved the principle's inherent dead-angle problem. Based on this method, we simulated the configuration of parameters for designing a system with scalability for dexterous 3D motion. We implemented an actual system and applied a parallel computation structure to increase the tracking speed. We also built some examples to show how well our system works for actual situations.