, Jan. 29 -- Nestled in Japan's Hakone region, Owakudani is a steaming volcanic valley famous for its black eggs, known locally as kuro-tamago.

Boiled in sulphur-rich hot springs, the eggs turn jet black, and local legend promises that eating one adds seven years to a person's life.

The story dates back over a thousand years to Kobo Daishi, a revered Buddhist monk and scholar, who encouraged locals to consume eggs boiled in the valley's hot springs to promote health and vitality.

Over time, this belief evolved into the enduring legend of the seven-year lifespan boost.

Owakudani, about 90 km from Tokyo, attracts visitors with its dramatic landscape of hissing vents, steaming fissures, and rocky terrain.

The valley's geothermal activit...