This paper analyses how the conceptual and therapeutic formation of Japanese traditional medicine (Kampo) has been socially constructed through interactions with popular interpretations of illness. Taking the example of emotion-related disorders, this paper focuses on the changing meaning of constraint (utsu) in Kampo medicine. Utsu was once a name for one of the most frequently cited emotion-related disorders and pathological concerns during the Edo period. With the spread of Western medicine in the Meiji period, neurasthenia replaced utsu as the dominant emotion-related disorder in Japanese society. As a result, post-Meiji doctors developed other conceptual tools and strategies to respond to these new disease categories, innovations that continue to influence contemporary practitioners. I begin this history by focusing on Wada Tōkaku, a Japanese doctor of the Edo period who developed a unique theory and treatment strategy for utsu. Secondly, I examine. Yomuto Kyūshin and Mori Dōhaku, Kampo doctors of the early twentieth century, who privileged neurasthenia over utsu in their medical practice. The paper concludes with a discussion of the flexibility and complexity of Kampo medicine, how its theory and practices have been influenced by cross-cultural changes in medicine and society, while incorporating the popular experience of illness as well.