The Titles of Monarchs in Medieval Japan

In previous studies, it has been widely accepted that after the title tennō 天皇 first appeared for the Japanese monarch, it was no longer commonly used in the middle Heian period. However, this view is inaccurate because the distinction between titles for deceased or retired monarchs and those for reigning monarchs was not clearly made in those discussions. This paper analyzes the titles used by the nobility for the monarch after the middle Heian period, based on historical sources, and examines the differences in authority and roles associated with those titles. Titles such as tenshi 天子, tennō, and kōtei 皇帝, which had been prescribed in the ritsuryō 律令 codes, were already being used interchangeably by the 8th and 9th centuries. By examining the diaries of the nobility from the 10th to the 15th centuries, it is found that, in the 10th century, reigning monarchs were often referred to with terms like jō 上, kinjō 今上, and shujō 主上. In many diaries, shujō appears far more frequently than tennō. However, tennō also appears with considerable frequency in other diaries, so it would be incorrect to claim that the title tennō was never used, or was rarely used, during the medieval period. Examining several examples, it seems likely that the title tennō was used for the Japanese monarch in the sense of a formal, institutional figure overseeing state affairs and ceremonies, a role that has existed since ancient times. Expressions such as kōke or kuge 公家, kokuō 國王, and kokushu 国主 also emerged in the late ancient period and early medieval period, reflecting the monarch's role as a ruler. However, after the establishment of the Kamakura shogunate, the term kōke evolved to represent the aristocratic or non-military nobility, in contrast to the buke 武家 or jike 寺家. Terms like kokuō and kokushu began to be used more specifically to refer to the Emperor Emeritus or the de facto rulers, such as the Hōjō clan 北条氏, who held power in the shogunate. As a result, the title tennō continued to be used to refer to the monarch's abstract, fundamental role and position as the sovereign ruler.