TOKYO — At first glance, an undersea rail tunnel connecting Japan’s main island of Honshu to its northern neighbor of Hokkaido would seem like a logistical blessing for chipmaker Rapidus and its plans to produce cutting-edge semiconductors near the top of the country.

But trains are banned from carrying potentially dangerous substances such as high-pressure gas or inflammable liquids through the 54-kilometer Seikan Tunnel, which opened in 1988 and includes a 23-km section under the Tsugaru Strait.

AloJapan.com