Although the modern name Shunan appeared on the map of Japan quite recently, on April 21, 2003, as a result of the merger of the cities of Tokuyama and Shinnanyo, and the towns of Kumage and Kano, the history of these lands goes back centuries. The historical core of the region is the former city of Tokuyama, which played a significant role in the life of the prefecture for centuries.
The actual beginning of the city's development as an important center can be considered 1650, when the Tokuyama Domain—a branch of the powerful Mori clan—was formed. It was then that a castle was built here, around which a classic castle town (jokamachi) began to take shape, attracting samurai, artisans, and merchants.
The region's development was determined by several strategic advantages. Its location on the shores of the Seto Inland Sea provided a natural harbor protected by islands, which favored the development of seafaring. In addition, the important historical Sanyodo road passed through these lands, connecting the western part of Honshu with the country's political center, making the city a vital transport hub.
During the Edo period, the region's economy was based on traditional industries: local residents were actively involved in fishing and salt production. However, with the onset of the Meiji era and the beginning of Japan's modernization, the region transformed rapidly. Thanks to its convenient bay, a large naval fuel depot was established here in the early 20th century, laying the foundation for Shunan's transformation into one of the leading industrial centers of modern Japan.