Getting here requires a long train ride, but those with JR Passes can make use of the wonderful overnight sleeper from Tokyo: the Sunrise Seto (サンライズ瀬戸). You can either sleep on a partitioned, carpeted floor section for free between Tokyo and Takamatsu (in Shikoku), or upgrade for about 10,000 yen to an actual room. Either way, this makes for a fun overnight and leaves you relatively well-rested when you reach Shikoku. Be warned: from Takamatsu, the train to Matsuyama takes another three hours. Once there, however, the bath won't disappoint, and there are plenty of other things to do and see in Matsuyama once you're done with your soak. It's worth noting that you should head to the Dougo Onsen Honkan, not the newer Dougo Onsen resort area. From the main station you can take a streetcar that arrives at Dougo Onsen in about 15 minutes. Enjoy!