Masses of Japanese living in exile, with some even turning to indiscriminate acts of terrorism, is an unimaginable situation–unless Japan sank deep into the ocean 25 years ago, forcing the entire population to scatter across the globe to survive. With no native soil to stand on, all Japanese have become refugees.

That spine-chilling scenario unfolds in the recently published “Nihon Chinbotsu Dainibu” (Japan Sinks, Part II, Shogakukan, 1,890 yen), by Komatsu Sakyo, Japan's leading science fiction writer, and writer Tani Koshu. The book is a sequel to Komatsu's 1973 “Nihon Chinbotsu,” whose two volumes sold nearly 4 million copies.