At a weekend pop-up restaurant in Tokyo's upmarket Roppongi district, those who ask for soup might get a salad, while those who order a hamburger could be served pasta.
There should, however, be no complaints at what is quirkily called the Restaurant Of Order Mistakes. Its team of wait staff comprises 17 dementia patients, and executive committee member Shiro Oguni, a television director, said he hopes to foster a spirit of tolerance, empathy and acceptance towards dementia patients.
Estimates show that almost one in five senior citizens in Japan suffers from dementia, with numbers set to rise as the nation grapples with a fast-ageing population.
This is the three-day pop-up restaurant's second run, following a similar event in June. Limited tickets have been set aside for walk-in customers, with the bulk reserved for donors in an online fund-raiser that collected almost 13 million yen (S$158,000) - nearly 5 million yen more than the initial target.
The event ends today as Japan marks Respect For The Aged Day with a public holiday.
The Statistics Bureau, in data released yesterday in line with Respect For The Aged Day, said the proportion of the elderly to the total population stands at 27.7 per cent.
Japan defines its elderly as those aged 65 and above.
This figure, a new high, is projected to reach 35.3 per cent by 2040. Those who are 90 years old and above also crossed the two million mark for the first time.
Last Friday, the Health, Labour and Welfare Ministry said the number aged 100 years and above has risen to a record 67,824 people, of whom nearly nine in 10 are women.
Japan's oldest woman, Ms Nabi Tajima, 117, was born in August 1900 in Kagoshima in the south-west. Last Saturday, she took over the title of the world's oldest woman after the death of Jamaican Violet Mosse-Brown, who was born in March 1900.
Its oldest man, Mr Masazo Nonaka, 112, hails from northern Hokkaido and was born in July 1905.
The data showed that nearly 12 per cent of Japan's workforce are seniors who choose to continue working. Most Japanese firms require full-timers to retire at 60, but they can extend for five years on a contractual basis with reduced terms.
As of last Friday, there were some 7.7 million seniors in the workplace. Three in four of them are so- called "irregular workers" who do part-time or contractual work.
These numbers, too, are set to rise as the elderly look for ways to spend their time and to supplement their household savings.
Two geriatric groups are now lobbying Tokyo to add 10 years to its definition of elderly. Japan's life expectancy last year was 87.1 years for women and 81 years for men.
Their rationale, as Dr Yasuyoshi Ouchi, 68, told a recent briefing, is for Tokyo to acknowledge the "rejuvenation" of Japan's seniors in their physical and intellectual health amid advancing medical care, nutrition and sanitation standards.
But critics of the plan are concerned that any rise in the elderly age definition would lead to a delay in pension payouts and affect those on social assistance.
Sociologist Emi Kataoka of Tokyo's Komazawa University told The Straits Times: "An old man who is able to work will have to continue to pay taxes, and if the plan is realised, it means a shift towards a system in an ultra-ageing society where social security support is propped up by other elderly (citizens)."
Social safety nets must be enhanced before such a proposal can be considered, she said, adding: "If pension annuities are not paid out until 75, there is the risk that those aged from 65 to 74 who are ill or are unable to work will be left in limbo."