The above document is called a Jamae Mungi (自賣文記 – 자매문기), which was a contract used in Joseon Korea to sell oneself and/or one’s family members into slavery. It was an option available to Koreans in dire circumstances. You can find the above document here.
The documents included the date of sale, the names of the buyer and seller, the reason for the sale, the selling price, the name of a witness, and a signature. If the seller could not write, he or she could draw an outline of his or her hand (手掌 – 수장). The document also had to be stamped by a local official.
In the above document, which was made in 1832, the man was selling himself, his pregnant wife, the unborn baby, and their 2-year-old child because “life was difficult.”
Also, the Dong-a Ilbo had a very interesting article, here, about a man who sold himself into slavery in 1815 to pay for a proper funeral for his father, who had become a “wandering beggar” after a flood had destroyed their home. Here is how his document started out:
“My household was originally poor, and we had no close relatives. So when the big famine hit us in 1815, my father left home to wander as a beggar. He ended up dying several hundred ri from home.”
It is a tragic story, but stories like that and the old custom of selling oneself or one’s family members into slavery during dire times may help explain why so many Koreans became “comfort women.”
“Frog in the Well” also talks here about the custom of “Jamae” and the Donga Ilbo article.