The former Minister of Law refers to the Minister of Law in the kingdom of Kei upon Youko Nakajima's ascension to the throne. The Minister is depicted as a woman in the anime; the Minister of Law's gender in the novel is not stated.
The Minister of Law is aligned with Seikyou's faction in the court, thus she does not enforce the law if it will further solidify Seikyou's power in court. In the anime, she openly undermines Youko's ability to discern who can be trusted in court by suggesting that ministers in the faction opposing Seikyou are against Youko and her attempts to reform the court.
In both the novel and the anime, Youko suspects that she cannot truly trust any of the ministers in her court as they are either aligned with Seikyou or opposed to him. In light of the accusations against Koukan, the governor of Baku, and the Sankou and the death of the Taisai, the minister serving as the Palace Administrator and Seikyou's most vocal opponent, Youko immediately exiles Koukan and the Sankou and demotes all the members of Seikyou's faction. Seikyou is forced to become the Palace Administrator while the Minister of Law, along with the Ministers of Rites and Lands, are demoted to the positions of the Sankou.
In the anime, the Minister of Law remains as Seikyou's most visible ally and conspires with him and takes advantage of Youko's disappearance from court to maintain their power. At the end of both the novel and the anime, the Ministry of Law is threatened by Youko into ensuring that the law is properly enforced and punishment is delivered, reminding the Minister of Law and the Ministry of Justice that she was responsible for ordering the arrest of Seikyou and his cronies. The anime depicts the events similarly, with the Minister of Law's response to Youko's threat being quickly silence with the same reminder of that the monarch had ordered Seikyou's arrest.