>>1517828This would be the route, the lateral line going from Matsuyama to Tokushima via Takamatsu, a branch going to Okayama linking Shikoku with the main island. and a branch heading to Kochi in south shikoku. Part of the plan would also be in the future to extend all the way to Kyushu in Oita through western Shikoku (a project that would probably cost literally hundreds of billions), as well as another tunnel/bridge going through Awaji Island all the way to Kobe/Osaka.
Here's a good primer on the project, you can use the auto translated subtitles if you don't understand JP
https://www.youtube.com/watch?v=XELk5prsYzI 