sentences:  A fifth-batch 3000 V series six-car set entered service on the line on April 9, 2017, with a total of seven sets scheduled to be introduced by 2022, replacing the earlier 3000A series trainsets.In 1965, construction on Line 1 and Line 3 of the subway began.The subway was inaugurated on September 16, 1972, when the 5.2 km long initial section of Line 1 opened between Kami-Ōoka and Isezakichōjamachi stations.