Kim Yak-sŏn (Korean: 김약선; Hanja: 金若先; fl.
As the father-in-law of the future king, Kim was appointed as vice commissioner of the Security Council (추밀부사; 樞密副使; ch'umilpusa).
However, Kim's wife, the daughter of Ch'oe U, committed adultery with a male servant.
When Kim Yak-sŏn discovered his wife's affair, to cover up the incident she made a false accusation against her husband.
The exact nature of the accusation has not been recorded in history, however it is thought that it must have been equivalent to treason for Ch'oe U to sentence his own heir apparent to death.