At midnight every night, Shoko Ohara, a 39-year-old construction company employee, drives to the station to pick up her hard-working husband Takeshi, an engineer. The two chat during the 10-minute ride to their suburban home, and while Takeshi takes a bath, Shoko warms up his dinner in the kitchen. She then goes upstairs to their roomy bedroom and falls asleep in a comfortable double bed -- where she spends the night alone.

Throughout their 13-year marriage, the couple has rarely slept in the same room, except for a few months after moving into their upmarket house in the city of Okegawa, Saitama Prefecture, for which they specially purchased the double bed.

In the two years before that, they took turns sleeping in a single bed in the bedroom and on a futon in the tatami room in their apartment. The new double bed was spacious and comfortable, but soon Takeshi began sleeping separately, either in his study next door or in the tatami room downstairs.