Ōkunoshima is a small island located in the Inland Sea of Japan. The island is called Usagi Shima (Rabbit Island) due to the number of apparently tame rabbits that roam the island.
The dark side of this island is that this is where during WWII, poison gas was made for the war with China. The cute side is all the rabbits, whose origins are not really known but speculated upon.
Japan Has an Island Full of Rabbits — But This Small Island Has a Dark History by Andrew Amelinckx (March 21, 2017)
Island of Bunnies and Poison – Ōkunoshima documentary
The Mystery of Rabbit Island