JR Shikoku doesn't advertise this for some reason on its English language website, perhaps assuming that most visitors from overseas will already have the JR railpass to cover the whole country, or will not want to do extensive train travel in Shikoku.
Unlike the JR pass, there are no residency restrictions, meaning that those of us who live in Japan can make use of this pass.
3 days unlimited use of JR Shikoku's network for 15,700 yen. This includes all express services. It is also possible to use some JR Shikoku buses.
Can be purchased at any JR Shikoku ticket office.
Although Shikoku is an island, there are three separate series of bridges onto the island, one of which is shared with the railroad as well.
The first is the Shimanami Kaido from Hiroshima prefecture, the second is the Seto-Ohashi road/rail bridge from Okayama prefecture, and the third one goes through Awaji Island to Kobe.
From Okayama station on the mainland, there are direct trains to Matsuyama, Kochi and Takamatsu.