Direct services from Okayama now operate with the completion of the Great Seto Bridge system, over which the Honshi-Bisan Line travels.

The Marine Liner rapid service connects Takamatsu with Okayama via the Seto-Ōhashi Line.

Local service typically serves one of four sections of the Yosan Line, generally divided at Kan'onji, Iyo-Saijō, and Matsuyama.

The first segment of the line, from Tadotsu to Marugame, was constructed by the Sanuki Railway Co. and commenced operation in 1889.

The line was extended west from Tadotsu in sections commencing in 1913, reaching Matsuyama in 1927.

The 'direct line' between Mukaibara - Iyo Ozu (including the 6,012m Inuyose tunnel) opened in 1986, incorporating part of the former Uchicko branch and shortening the route by 6.3 km.