This paper introduces the studies conducted from the 1980s to the 2000s on the Daimyo clan of the Tokugawa period, along with the introduction of the research history on the master-servant relationship. The introduction of the research history mainly deals with the studies of Asao Naohiro (朝尾直広), Kasaya Kazuhiko (笠谷和比古), Takano Nobuharu (高野信治), Fukuda Jijeuru (福田千鹤), Fujita Datsuoh (福田达生), Miyake, Masathiro (三宅正浩). and discusses the distinctive characteristics of these studies from the 1990s, 1980s, and 2000s respectively. The following points have been confirmed by these studies. First, the relationship between Daimyo as an individual and a Daimyo courtier was not necessarily static. Secondly, the Daimyo clan was an object of loyalty for Daimyo courtiers. Nowadays, it is very difficult to discuss the master-servant relationship of the Tokugawa period without distinguishing Daimyo as an individual from Daimyo as a clan.