Christopher of Yellow Productions has a great video about renting cars in Japan. He made this video on his Hokkaido visit, but it is very helpful and useful for when you come to Kagawa and rent a car to explore Shikoku!
And here is another video that is very important to take a look at so you are familiar with the Japanese road signs you will see as you travel along. You may know these already, but a bit of a refresher is not a bad idea before you get behind the wheel. Check out this great video by the Japanese Language and Culture Channel: