The Tokyo Metro Fukutoshin Line , formally the No. 13 Fukutoshin Line , is a 20.2-kilometer (12.6 mi) subway line operated by Tokyo Metro in west-central Tokyo and Wako, Saitama, Japan. The newest line in the Tokyo subway network, it opened in stages between 1994 and 2008. On average, the Fukutoshin Line carried 362,654 passengers daily in 2017, the lowest of all Tokyo Metro lines and roughly one third of its sister Tokyo Metro Yūrakuchō Line (1,124,478).