While both JR and Nankai operate trains to Wakayama and to Kansai Airport, neither route is ideal. For JR, trains must use the Osaka Loop Line past Tennoji Station, both creating and being affected by delays on that line, and bypassing JR Namba Station, the company's closest link to Osaka's commercial center. Additionally, express trains to Shin-Osaka and Kyoto must use the Umeda Freight Line, bypassing Osaka Station entirely. For Nankai, all trains go direct to its terminal in Namba, precluding links to points further north. The issue surrounding Osaka Station for JR is set to be alleviated in fiscal 2022 with the opening of the first section, which will terminate at new underground platforms of Osaka Station on a route replacing the aboveground Umeda Freight Line. Without constructing an entirely new line through central Osaka, however, the other problems remain. Plans were drawn up in the mid-2000s to alleviate the problems for both companies through the construction of a new underground line, primarily under the north-south thoroughfare Naniwa-suji, branching at its south end to connect both the Yamatoji Line terminal at JR Namba, and a Nankai line, with Shin-Osaka via a new underground route through what was then the Umeda Freight Terminal. The Umeda portion of this plan was eventually incorporated into Phase II of the Osaka Higashi Line, with provisions in place for eventual construction of the Naniwasuji Line itself. Early plans for Nankai called for moving the Shiomibashi Line underground and connecting to the Naniwasuji Line via Shiomibashi Station, but the company ultimately rejected this routing in favor of one via a new underground station at Namba.
Current Plans
Current plans are to begin construction once the Osaka Higashi Line opens to Osaka Station, with completion anticipated in spring 2031. Total construction costs, including provisions for the line at Kita-Umeda, are projected to total some 330 billion yen. In the interim, JR passenger trains will use a single-track freight spur from Osaka Station to join the Osaka Loop Line at Nishi-Kujō, much as they do now.
Stations
Excluding the northern terminus at the new underground platforms of Osaka Station and the existing JR Namba, three stations are to be constructed: Nakanoshima, Nishi-Hommachi, and Nankai Shin-Namba. The line will also pass through the vicinity of Fukushima, Shin-Fukushima and Nishiōhashi, although no stations are currently planned for these locations.
