], upper-class men in China, Japan, Korea, and Vietnam often had more than one spouse to ensure the birth of a male heir to their assets and titles.
Under this system, a man was allowed one official wife, called a zhengshi (正室, pronounced seishitsu in Japanese, lit.
In the Tang dynasty, any man who had more than one di wife would be considered to be bigamous and would be liable to one year of penal labor.
The woman involved would also receive a slightly less severe punishment unless she could prove she had been cheated into the marriage.
Based on social standards, the di wife's major responsibilities were managing all shu wives and taking care of them like her younger sisters.
However, there were three conditions, known as "three exceptions" (三不去), that forbade a man from ever divorcing his wife even if she did commit any of the above seven sins.