Due to his father's death on behalf of the nation, Song Yu-in was granted the rank of executive captain (산원; 散員; sanwŏn) via protected appointment.
[1] Song rose through the ranks to become a commander of the Household Bureau of the Crown Prince (태자부지유; 太子府指諭; 't'aeja-pu chiyu) then general of the guards (위장군; 衛將軍; wi changgun).
[1] However, when he was unable to deal with local revolts, he feigned illness and resigned from the role, and was replaced by General U Hakyu.
[3] On January 23, 1175, Song Yu-in was appointed as vice commissioner of the Security Council (추밀원부사; 樞密院副使; ch'umirwŏnpusa) and the minister of war (병부상서; 兵部尙書; pyŏngbu sangsŏ).
In 1179, he impeached Confucian scholar-officials Mun Kŭk-kyŏm and Han Mun-jun, demoting them from their positions at the Security Council.