The Sanin Main Line is a railway line in western Japan, which connects Kyoto and Shimonoseki, Yamaguchi, operated by West Japan Railway Company. It is the major railway line of the San'in region, approximately paralleling the Japan Sea, crossing Kyoto, Hyōgo, Tottori, Shimane, and Yamaguchi prefectures. The main portion from Kyoto to Hatabu is the longest single continuous railway line in Japan at 673.8 km (418.7 mi), although no regularly scheduled train operates over the entire line.

Shimonoseki is a city located in Yamaguchi Prefecture, Japan. As of 30 June 2023, the city had an estimated population of 248,193 in 128762 households and a population density of 350 persons per km2. The total area of the city is 716.18 square kilometres (276.52 sq mi). It is the largest city in Yamaguchi Prefecture and the fifth-largest city in the Chūgoku region in terms of population. It is nicknamed the "Fugu Capital" for the locally caught pufferfish, and is the largest harvester of the pufferfish in Japan.