There is also some overhyping of Japan's extended lifespans. A statistically significant number of japan's very old have been linked to various forms of fraud, enough to impact average lifespan calculations. After several horrific cases (deaths not being reported) a nationwide effort was made to locate the very old (>110). Many have not been located. Many of those small japanese villages with phenomenally old populations were a myth. People were staying on the books long after death.

"More than 230,000 elderly people in Japan who are listed as being aged 100 or over are unaccounted for, officials said following a nationwide inquiry."

https://www.bbc.com/news/world-asia-pacific-11258071