During the construction of the easternmost section of the Sankyū Main Line (most of what is now the Yamada Line), another private railway company, Ise Electric Railway ("Iseden"), was constructing another line right alongside that would eventually link with and was known as the Iseden Main Line. The two lines opened within just a few weeks of each other in 1930 which led to there being three parallel lines (the third being the Sangū Line) owned by three different companies running between Matsusaka and Ujiyamada. Sankyū and Iseden pledged to work together to ensure they both prospered, however both companies soon began a merger struggle and, in 1936, Sankyū won the battle and acquired Iseden and its lines. The Iseden Main Line became known as the Sankyū Ise Line.