Bradley K Martin's 2004 book Under the Loving Care of the Fatherly Leader is based on a combination of visits to North Korea, research and interviews with defectors carried out in the early 1990s. Martin writes that Kim Il Sung was not just interested in pleasure, but also in rejuvenating himself through absorbing a young virgin's ki, or life-force, during sex. He believed that having sexual relations with young women would increase his jing and have the effect of enhancing his life force, or gi (Chosŏn'gŭl: ; Hanja: )
