It's been a bit of an odd fall in Japan. First, the cherry blossoms – "tricked" by typhoons – bloomed extra early, sending part of the country into a pastel pink haze months before schedule. Now, an entire island off the north coast of Hokkaido has gone missing – and no one seemed to notice.

The island: Esanbe Hanakita Kojima

Population: zero

Esanbe Hanakita Kojima is one of 158 uninhabited islands in the area only formally named by the Japanese government in 2014, an attempt to lay claim and secure the territory for Japan. Partly because just west of Esanbe Hanakita Kojima is a series of islands – called the Kurils – whose ownership has been heavily disputed between Japan and Russia for centuries.

Astonishingly, its disappearance was not noticed until September when an author called Hiroshi Shimizu visited the area to start work on a new project, a follow-up to his picture book on Japan's "hidden" islands. On seeing (or rather, not seeing) the missing island, he notified the local fisheries cooperative. They then deployed boats to check the status of Esanbe Hanakita Kojima.

Indeed, the area just 500 meters (1,640 feet) off the coast of the village of Sarufutsu, Hokkaido, showed little signs of any landmass. The only clue to suggest Esanbe Hanakita Kojima's existence was what looks like a "rocky shoal at the island's former charted position", The Maritime Executive reports.

But a little more digging revealed that yes, there was indeed a Esanbe Hanakita Kojima and it stood at just 1.4 meters (5 feet) above sea level. It appears on a sea chart from 1987 and is remembered (not fondly) by some of the older local fishermen.

"Around a decade from 1975, there was a small island around there, and we stayed clear of the area," one told Japanese paper, The Asahi Shimbun. 

So, it existed. What happened?

It's not the first time an island has "disappeared". In fact, only last month a category 5 hurricane swept East Island, Hawaii, straight off the map and in the last half-century or so, the Solomon Islands have shrunk by five, while Micronesia has lost eight islands due to sea-level rise and wave exposure. (And as sea levels continue to rise, we can expect to see more "missing" islands in the future.) 

In this case, experts believe it was a tricky combination of wave action and drift ice that caused it to erode over time, but an investigation this month will hopefully provide more clarification to Esanbe Hanakita Kojima's status. As for Japan, this news does mean that its exclusive economic zone (EEZ) will shrink. Fortunately, it's only by half a kilometer.