In the context of JAV (Japanese Adult Video), "Reducing Mosaic" or "Reduced Mosaic" (often referred to as RM ) describes a video that has undergone post-processing to thin or smooth out the required digital pixelation.
Rather than a traditional narrative story, this term is usually a technical identifier for a digital file. If you are looking for a creative story inspired by the idea of high-tech digital restoration or unmasking hidden details, here is a short piece: The Signal in the Static ssis698 4k reducing mosaic full