TSUCHIKURE, Japan -- Jeffrey Irish, a 48-year-old American, is the unlikely village chief of Tsuchikure, a remote farming hamlet in Japan's southern Kyushu island. The tall, even-tempered Californian got the position because he satisfies the post's main requirements: He hears and sees well.

In Tsuchikure, where the average age is 77 (if you don't count him and his family), that makes Mr. Irish one of only three residents qualified for the job. He spends his days keeping track of the physical and mental decline of the 24 elderly...