When talking about frontiers and borderlands, the naming of places becomes utterly loaded with political implications. In this book, I have tried to preferentially use the toponyms used in the eras under examination, as far as possible without confusing the reader too much. Certain places have been known by a palette of more or less obscure names over time, especially places that have been claimed discovered or incorporated by different actors at different times, like the Bonin Islands, which have no indigenous name to fall back on. In no instance are my choices – which are generally oriented at historical accuracy – the expression of an opinion on territorial claims by any present-day actors.

Representation is always a balancing act. The overwhelming number of actors in this book are men – sailors, bureaucrats, cartographers, businessmen, and ruffians. This is partly due to the gendered nature of seafaring and early modern academe, and to an archival bias in both Western and Japanese contexts. As is common in the modern Japanese language, Japanese names are given in the order family name, then first name throughout the book. For commoners, it was not formally allowed in the early modern period to use last names in public. Accordingly, commoners appear in official records with simple first names and, if necessary, a qualifier such as their home village or domain, as in Chōhei from Tosa. Notorious officials sometimes carried the same first and last names over generations, to which one or several qualifiers could be added, as in the example of Nirayama Magistrate Egawa Tarōzaemon Hidetatsu “Tan’an,” or the Nagasaki Magistrate Suetsugu Heizō “Shigetomo.” Official ranks in early modern Japan are generally difficult to translate, literally or by meaning, since their function and naming often had no obvious correlation, as is true, for example, for “Minister of the Right” Iwakura Tomomi. Accordingly, there is no standard translation for most positions. In the interest of general intelligibility, I follow the strategy of translating each rank in a way that conveys a sense of its actual function.

The Japanese calendar counts the years elapsed since the periodical proclamation of a new political era called nengō or gengō. Between 1600 and 1868, the Japanese calendar is divided into thirty-six eras with individual era names. The year-count restarts with every era change, as it still does in contemporary Japan: The year 2025 is the year seven of the Reiwa era. As has been common since the Meiji era (1868–1912), the era change from the Heisei (1989–2019) to the Reiwa era (2019–) marked the imperial succession from Emperor Akihito to his son, Emperor Naruhito. In the early modern period, however, era changes were effectuated independently of investiture and marked a change in political strategy.

The calendar followed a lunar measure until its harmonization with the Gregorian calendar in 1873. Until that time, the Japanese year, which usually began during the Gregorian January or February, relied on the occasional insertion of intercalary months as an astronomical adjustment to the observed season. Accordingly, the dates found in Japanese sources cannot be translated linearly into a Gregorian correspondent, the dates matching up differently every year. It may be confusing that the first month, ichi-gatsu, of the lunar calendar does not correspond to January, or ichi-gatsu in the modern Japanese meaning, but the distinction is important: Whereas the nineteenth day of the third month in the year Kaei 4 (1851) corresponded to April 20, the same nineteenth day of the third month in the following year Kaei 5 (1852) corresponded to May 7. For the sake of simplicity, I list years in the Gregorian calendar, but keep specific dates in spelled-out, numbered months as they are given in the Japanese sources. In the case of ambiguity, I add a Gregorian rendering, naming the months, as necessary.