Mixed Reality (MR) can be used to visualize three-dimensional (3D) sound fields in real space. In our previous study, we proposed a sound intensity visualization system using MR. The system visualizes the flow of sound energy in a stationary sound field by measuring sound intensity. However, room impulse responses (RIRs) are essential data when investigating the sound field of a room. Therefore, to demystify the time variation of the sound field, it is crucial to visualize the spatial distribution of RIRs. However, the measurement of multipoint RIRs requires considerable time and effort and a large microphone array. In this paper, we propose an MR visualization system for RIR mapping on two planes based on dynamic RIR measurement using a moving microphone. The proposed system simplifies the measurement of RIRs at multiple points owing to the dynamic measurement capabilities of a hand-held microphone. In the simulation experiment, the RIRs on the grid points were estimated from the microphone signal using the moving path of the microphone. The estimated results were visualized by the animation of RIR maps in real space using MR. From the experimental results, the MR animation of RIR maps on the two orthogonal planes can help demystify 3D sound propagation.