It operates Japan 's shortest independent railway line largely underneath Narita International Airport .
Japan 's shortest independent railway line is the 2.2 km Shibayama Railway Line between Higashi - Narita Station and Shibayama - Chiyoda Station .
It operates Japan 's shortest independent railway line , the 2.2 km Shibayama Railway Line between Higashi - Narita Station and Shibayama - Chiyoda Station , largely underneath Narita International Airport .