Traditionally, an implementation of mixed reality systems requires tight and accurate spatial/visual registration between the real and virtual objects. Any meaningful interaction is only possible within this "tightly" coupled mixed reality world. Thus, the degree of this spatial and explicit registration has been regarded one of the most important factors in the usability of mixed reality systems. In this paper, we argue that the "loose" and "implicit" association may be sufficient to establish a unified mixed reality space. More specifically, we introduce, what is called, the "Loosely coupled Mixed Reality (LMR)," in which the user maintains a unified mixed reality space with minimal explicit association cues between the real and virtual space. To help this binding process, an implicit but intuitive environment metaphor between the two realities is used. We ran a simple experiment to compare the task performance, as a measure of the coherency of the perceived mixed reality space, of our approach to the standard augmented reality. Our results have shown that despite the lack of visual/spatial registration feedback and thus having to rely on the imagination of the user, the perception of the mixed reality space and usability of LMR did not degrade much from those of the conventional AR. LMR is a new pragmatic form of mixed reality medium with reduced requirements for exact tracking and rich visual feedback, especially suitable for mobile devices.