Considering how expensive housing is in Japan, foreigners just off the boat tend to be surprised that there isn't more communal living going on. Most Japanese apartments, even the larger ones, are not really adequate for communal living the way apartments in the West are, and in any case Japanese landlords tend to frown on renting out properties to multiple persons if those persons are not married or otherwise related. Consequently, there's no vocabulary for shared dwellings, much less a market.
That is until now, and it appears to be a market-driven development. The explosion of vacant rental properties in the larger cities have prompted some real estate companies to take it upon themselves to offer what is being called "share houses," meaning houses and apartment buildings with communal living rooms, kitchens and bathrooms. These companies rent out the bedrooms as they would apartments, and the practice has caught on so much so that the media is covering it as a trend, as seen on our comrade blog, Japan Pulse.
The main appeal is economic, but the real draw is social, especially among women who don't feel safe living by themselves in one-room apartments in the city. Share houses offer privacy with the option of interpersonal interaction. The model for this kind of living is Share Place Gotanno in Adachi Ward, Tokyo. Formerly a company dormitory (most share rooms are), the building has been converted by the Tokyo Electric-affiliated housing renovation company ReBita into 45 rooms centered around a living and dining area that is the equivalent in size to three households' worth. Consequently, the kitchen has three large refrigerators. Each bedroom is the size of about seven tatami mats and includes an air conditioner, a bed, a desk, and a storage unit. The monthly rent is from ¥58,000 to ¥63,000, there's a "management fee" of ¥13,500, and a ¥50,000 deposit (¥30,000 refundable) is required. There's also a ¥36,000 "processing fee" and a one-time insurance fee of ¥8,000. Foreigners are welcome.