Twenty-five-year-old Sotaro Ito lives in a 9.46-square-meter apartment with a loft in the capital's retro-hip Koenji district.

His apartment looks more like an office cubicle, with a desk and computer chair dominating a third of the room. A reading pillow is propped up against one of the walls, but there isn't enough space for him to stretch out his body. A clothesline rope stretches between two wall sconces for him to dry his laundry, and his kitchen is equipped with a small sink and a single induction cooktop.

What his room lacks in space, however, is made up for in height. The ceiling of the apartment is 3.6 meters high and three windows have been built into the exterior wall, letting in plenty of light. A white ladder takes Ito up to a 4.5-square-meter loft that's 1.4 meters high — tall enough for him to sit upright. And unlike many single-person apartments with so-called "unit baths" that combine a toilet and bathtub, Ito's crib has separate rooms for a shower and high-tech bidet toilet.