"A nation of immigrants." Japan? The leading proponent of that vision has been Hidenori Sakanaka, former head of the Tokyo Immigration Bureau, current executive director of the private think tank he founded in 2007, the Japan Immigration Policy Institute.

His was long a voice in the wilderness as he called on Japan to welcome 10 million immigrants by 2050. In his writing, most recently a 2012 book titled "Jinko Hokai to Imin Kakumei" ("Population Breakdown and the Immigrant Revolution"), his irrepressible enthusiasm comes through in a partiality for words like "utopia" and "panacea." The problems his "revolution" would address are glaring. No nation, let alone an economic superpower, has ever faced population aging and population decline at anything like Japan's current pace. An influx of immigrants would repopulate, rejuvenate and globalize a naturally inward-looking country grown of late lethargic, complacent and old.

The trouble is, Japan is shy. Foreign faces, foreign languages, foreign ways make it nervous, and Sakanaka's call has generally been dismissed as quixotic.