Not only that, it's for a good cause -- helping to revitalise a city in northeastern Japan that was virtually wiped out by the March 11, 2011 tsunami.

"It's a mixture of soy sauce and ice cream, producing a well-balanced salty, yet sweet, ice cream which is perfect for the summer," said Kunihiko Shirokawa at Tokyo-based confectioner Hirota, one of the developers.

"We are planning another product for the autumn."

Hirota teamed up with Yamani Soy Sauce Co in Rikuzentakata, a city flattened by the massive waves, for a new twist on a flavour that has been around in Japan for some time.

Although it looks like typical vanilla, the ice cream has a distinctly salty and vaguely nutty flavour.

The collaboration was arranged by Seki Kinya, the head of Big Apple, an entrepreneurial consulting firm in Tokyo, who was inspired to do something to help after spending time cleaning up Rikuzentakata as a volunteer.

"I was in Takata during the clean-up efforts, and happened to meet an associate of Yamani," said Kinya. "Afterwards, the mayor talked about his hopes of revitalising local businesses and creating job opportunities. It was all a coincidence, really."

The cream puffs cost 150 yeneach, while the ice cream goes for 250 yen. A portion of the proceeds will be donated to non-profit organisations for aid efforts in Rikuzentakata. (Reporting by Teppei Kasai; Editing by Elaine Lies and Jeremy Laurence)

• A Permanent Economic Emergency