If sleepwalking is the condition of wandering through reality without realizing it, then dream-walking is the illness of traversing dreams while wide awake. In a world long past, dreaming gradually came to be regarded as a disease — a mental illness. "Dreaming is meaningless." Humanity, grown cold in the wake of rapid technological advancement, came to think this way. And so they began to prohibit the very act of dreaming. All manner of dream-suppressing medications — even vaccines — were developed. In this world, fantasy and dreams no longer exist.