FEATURE: Japanese nurse finds her true self in world's 'death zone'

CHILAS, Pakistan - By day, Naoko Watanabe works as a nurse. In her spare time, she ventures into the "death zone," where oxygen levels fall to about one-third of those at sea level.

Two years ago, the 44-year-old became the first Japanese woman to climb all 14 of the world's mountains above 8,000 meters.