Ōkunoshima (大久野島) is a small island located in the Inland Sea of Japan. It is also known as Usagi Shima because of the numerous feral rabbits that live here and it is for that reason that draws many people here. Nobody knows for sure how the rabbits got here. Some say they are the result of a scientific testing while others theorize that some children on a school trip left the original settlers here.

The island was a cultivated area until the Russo-Japanese War when ten forts were built to protect it. Three fishing families lived on the island.