Japanese people are the least satisfied with their sex and romantic lives, closely followed by South Koreans, a global survey by a French research firm showed.

The two Asian rivals are grappling with a similar demographic crisis with their chronically -- and dangerously, as authorities warn -- low birth rates.

The poll of 31 countries, conducted by Paris-headquartered Ipsos, showed this week that just 37 percent of Japanese respondents derive satisfaction from sex and romance, versus the 76 percent of top-ranked Indians and Mexicans.

Similarly displeased are South Koreans, whose sexual satisfaction was the second worst at 45 percent.

In June, Japan's health ministry described the nation's birth rate as "critical" as it stood at 1.20 last year, hitting a record low for the eighth straight year.

But Japan's rate is still above that of neighbor South Korea, which has the world's lowest at 0.72.

The same Ipsos poll also showed that South Koreans feel the least contentment from their "relationships with partners and spouses", with Japanese faring the second worst.

Asked how much they "feel loved" in life, 51 percent of Japanese said so, again the worst of all, slightly outranked by South Koreans and Italians at 63 percent.

The discontentment is partly the result of "the personality of Japanese people who aren't good at articulating their emotions and attitudes when it comes to romance", Ipsos said.

Among efforts to boost Japan's plunging birth rates is a dating app launched earlier this year by authorities in the capital Tokyo.

Users are required to submit documentation proving they are legally single and sign a letter stating they are willing to get married.