Ōkunoshima used to be home of several chemical plants, but now it's a tourist destination for those who love the wild bunnies who live there.
YouTube TheUwagaPies made a nice short documentary about the island's history:
Redditor EngVagabond has a cute album of his Ōkunoshima visit, including this little guy checking if a plastic cup still had any rabbit food in it:
According to YouTuber mybbbunny this is called the Rabbit Island Challenge, one of dozens on their channel: