Unfortunately not so many foreign and domestic tourists travel to Shikoku. Shikoku is connected with Honshu island by 3 large bridges but only one bridge has rails on it. Then, also no Shinkansen connection. If you are traveling with Japan Rail Pass from Tokyo or Kyoto, you have to take Hikari train bound for Okayama which runs hourly and then change to trains to Shikoku.
On the other hand, there are many places very worth to visit in Shikoku. Kagawa prefecture which is one of the four prefectures in Shikoku island and Kagawa is famous for Sanuki udon noodle. The prefectural capital Takamatsu is the second largest city in Shikoku island and definitely the most popular tourist attraction in Takamastsu is Ritsurin garden. Although it is not so famous as Kenrokuen garden in Kanazawa, garden with stones and trees might be more attractive than Kenrokuen.
Although it is not even known to Japanese as Kenrokuen, Ritsurin garden is probably the one of the best gardens must visit in Japan. Nearly 400 years of history, It has 6 ponds and 13 man-made hills, and it was the one of the gardens owned by daimyo; feudal lords who controlled their provinces. Ritsurin garden is the largest daimyo garden and famous for 1000 pine trees.
One of the best thing about Ritsurin garden is that you can hardly see the surrounding buildings, even though the garden is located in the city center of Takamatsu.