Keishitsu (Second wife) (継室)
Keishitsu means second wife.
In the history of Japan, there were many cases in which a woman of high standing became a keishitsu, as in the case of a lawful wife. It is a popular misconception that the most favorite concubine was raised to the position of the keishitsu after the death (or the divorce) of the lawful wife. This was very unlikely to happen considering the condition of an ordinary wife of a nobleman in Japan.