The Tokyo area is one of the most densely populated places on the planet. Very small properties have long been a feature of the urban landscape, but many modern "kyosho jutaku" showcase the expertise with which architects satisfy the requests of future owners. We join architect Koshima Yusuke as he visits these tiny houses, and sees for himself the clever ideas that are used to create a cozy living space. This time, a gradient of light spilling down a spiral staircase.