The Edo era (1603–1867) was a golden age for boatbuilding, and the 掘 essay explains why: political stability led to economic stability, and the burgeoning economy prompted a need for canals to transport goods, services, and people. As the 舟 piece shows, the Japanese actually devised boats with many styles and functions, including canal and river taxis. The 峠 article asserts that wealthy people traveled via commercial ships and that companies transported most goods domestically by boat. Indeed, the 垣 essay describes an odd-looking ship used to move items between Edo (the old name for Tokyo) and Osaka.

For thousands of years, Japan was isolated and homogeneous, particularly because the Tokugawa shogunate government closed the country from 1639 to 1854. The essays on 排 and 痘 show the costs of that, including the way this policy prolonged the smallpox crisis by delaying the arrival of vaccines in Japan. The essays on 謁 and 彰 describe how both Townsend Harris (the first U.S. consul general to Japan) and Commodore Matthew Perry signed treaties to change Japan's foreign trade policies, thereby opening the country to other cultures and sparking a westernization that delighted some Japanese and dismayed others.