Apparently there are nearly 11 regions overrun by cats in Japan. The 1st two cat islands we found in our search were Aoshima and Tashirojima.
Aoshima had at least 900 residents in the year 1945 but now very few live on the island. Cats were actually brought to the island to assist fisherman in combatting a mice issue. Fishing boats at times were overrun by mice. Over time the residents on the island decreased and the cat population increased.
Now in the 21st century there are 100's of cats and little to no actual people. The cats are simply feral and visitors come to tour the island and feed the cats. There are 2 boat trips to the island daily.
Tashirojima has a similar story, fisherman brought cats over to assist with a silkworm problem and over time the population has decreased leaving tons of feral cats. Guests can visit the island daily as there is a boat that visits the island twice a day.
There are some rules when visiting these islands and veterinarians pop by the islands to keep the felines in tip top shape. Dogs are never allowed on these islands.
A few other Cat Islands are :
Genkaishima was the largest cat island in Japan, but the cat populatio took a huge hit in the 2005 earthquake.
Muzukijima has beautiful orange groves with the best tasting oranges and tons of cats!
Iwaishima Island was a location that many wanted to place a nuclear plant, though the residents fought against it.
There are many more cat islands around Japan. If you love cats, you'll literally be in heaven!!