Japan has again shown off one of its greatest innovations - square watermelons.

For years consumers struggled to fit the large round fruit in their refrigerators.

But 20 years ago a forward-thinking farmer on Japan's south-western island of Shikoku solved the problem.

The farmer, from Zentsuji in Kagawa prefecture, came up with the idea of making a cube-shaped watermelon which could easily be packed and stored.

Fashion food

To make it happen, farmers grew the melons in glass boxes and the fruit then naturally assumed the same shape. Today the cuboid watermelons are hand-picked and shipped all over Japan.

But the fruit, on sale in a selection of department stores and upmarket supermarkets, appeals mainly to the wealthy and fashion-conscious of Tokyo and Osaka, Japan's two major cities.

Each melon sells for 10,000 yen, equivalent to about $83. It is almost double, or even triple, that of a normal watermelon.

"I can't buy it, it is too expensive," said a woman browsing at a department store in the southern city of Takamatsu.