The first subway system in Asia, Japan’s Ginza Line, opened December 30, 1927.

The Ginza Line was conceived by a businessman named Noritsugu Hayakawa, who visited London in 1914, saw the London Underground and concluded that Tokyo needed its own underground railway. He founded the Tokyo Underground Railway (東京地下鉄道 Tōkyō Chika Tetsudō) in 1920, and began construction in 1925.
Tokyo Metro

 

First Subway (1927)
From the Railroad Series No. 6
Issued by Japan Post in 2018

The website Constructing Tokyo’s first subway, 1925-1927. | Old Tokyo has a superb page on the history of the Ginza line, including photos of the construction.