We all know the Japanese remove their shoes before going inside. There's a rack for shoes just inside the door, and a bunch of slippers for use inside the home (and even these are removed when stepping on tatami mats). The house slippers are also removed at the threshold of the toilet; just inside, one finds special toilet slippers. In my experience, toilet slippers are often bright red, to distinguish them from the house; but these were the pair I found inside the WC at my ryokan in Nara.