A trip to an island — no matter what kind — should be on any good travel itinerary. Make your escape complete by heading to Oshima and spending time by the water.
If you're planning to go to Oshima in Takamatsu, make sure you leave time for some other sights too. After you've finished at this water-surrounded land mass, Teshima Art Museum is in the area and will keep you busy for a bit longer.