The topic of this article is the exceptional longevity in Okinawa. This phenomenon should be thoroughly validated at both the individual and population levels. This contribution analyzes the demographic data available for the population of Okinawa, in order to explain the presence of large numbers of centenarians. The mortality crossover obtained by comparing mortality rates in Okinawa and Japan could be attributed either to different behavior of the generations born before and after WW II, or to bad data. Arguments are presented in favor of both possible explanations. The reconstruction of the Koseki to replace the original, which was destroyed during WW II, could be a source of misreporting of age and would support the bad data hypothesis. Nevertheless, no concrete proof of invalid data has been found. Therefore, the author does not favor either of these explanations, but is calling for a more in-depth validation of longevity in Okinawa.