The first Japanese railroad construction goes way back 140 years to 1870.
Today, the SL Yamaguchi makes the 62.9 kilometer run in 2 hours between Shin-Yamaguchi and Tsuwano on the Yamaguchi line.
The Original Yamaguchi line was a narrow gauged private railroad company. It was called the "Dai-Nippon-Kido Co. Yamaguchi" between Shinmachi and Yuda, and it was opened during October 1908. But, this small railway was closed when the government railway Yamaguch line between Ogori and Yamaguchi was opened during February 1913. Later, JGR Yamaguchi line was fully opened on the 1st of April 1923. After WW2, Yamaguchi line saw service by Tsuwano depot's class D60s, but they were replaced by the class D51 during 1966. (You can see the preserved first D60 in the Yamaguchi Museum even now.)
In August 1979 a restored steam train was put into service to provide rides on practically all weekends. After Japan's regular steam operation was closed, this was the first case of a steam train being restored in Japan. The service was started by Umekoji museum's class C57 No.1. 2009 is the 30th anniversary for steam train restoration.
From: Restored Steam Trains of Japan
Near where I live, west of Tokyo, there is the Chichibu Railway, with a fabulous SL train service:
In the Kanto's mid-sized private railroad, the Chichibu Railway's first section, between Kumagaya and Yorii was opened on the 7th of October 1901. Originally the company was started as the Jobu Railway Co. with one C-Tank steam engine (Chichibu Railway's No.1, manufactured by Dubs Co.). The company name was changed to the Chichibu Railway Co. during March 1916. Chichibu Railway had a total of thirteen steam engines (Two were borrowed) in nine classes.
Chichibu Railway was electrified during 1922, at this time, the company owned six steam engines. These engines were retired by 1923, and sold or transferred to other railway companies. But a few engines remained as spare engines up to Jun 1934. Electric railway company's Chichibu Railway didn't have steam engines for the next 54 years.
Half a century later, a restored steam train was started from March 1988 by the C58-363. The train saw service between Kumagaya and Mitsumineguchi section. The nearest restored steam engine from Tokyo is the Paleo-Express.
There are many beauty spots on the "Nagatoro" river bank along the railroad line.
A personal favourite, Sayonara Daisuki na Hito from the Oigawa line in Shizuoka (since 1925). But that particular engine, used in the music video by Hana Hana, the C 56 44 appears to have been used in Thailand, back in the early 1940s?