South Korea’s ousted president and his free-spending wife have a unique distinction: In all the convolutions of high-level Korean corruption scandals, a former first couple has never previously been in jail at the same time

The former first lady, Kim Keon-hee, was packed off to the Seoul Detention Center after showing up for questioning on multiple charges of influence-peddling and stock manipulation while her husband, Yoon Suk-yeol, was president. No, she’s not in the same prison as Mr. Yoon, who was impeached, ousted as president, and charged with insurrection and treason for attempting to impose martial law last December.

Ms. Kim’s offenses may not seem so serious, but her enemies have been after her ever since her conservative husband was elected president by a slender margin in 2002. His foe then was the leftist Lee Jae-myung, who got his revenge by pursuing Mr. Yoon after the abortive coup and then getting elected president in a snap election in May.

Ms. Kim had faced numerous attempts to jail her, but she managed to stay out of jail with denials and explanations for allegations for which she now faces a trial that’s likely to go on for as long as her husband is tried in a separate court. The reason for jailing her while on trial is that she might destroy or tamper with evidence if left on her own — the same rationale for holding her husband after he had initially been freed while on trial.

The charges against Ms. Kim, said to have once worked in an expensive hostess club, resemble those against another ousted president, Park Geun-hye, who was jailed and convicted in 2016 and 2017, when Mr. Yoon was leading a prosecution team against her. Ms. Park, whom Mr. Yoon early in his presidency freed from a lengthy prison term, was said at the time to have been consulting with a trusted confidante, the daughter of a shaman or fortune-teller who had been close to Ms. Park’s father, the long-ruling dictator, Park Chung-hee.

The case of Mr. Yoon’s wife is intertwined with the Unification Church, the global ministry founded by Moon Sun-myung, who died in 2012. The special counsel team investigating her case charges Ms. Kim, among other things, with “colluding with a shaman over bribery allegations” related to the church, according to Seoul’s Yonhap News, in exchange for “luxury gifts, including a diamond necklace.”

The charges extend into a network of alleged political and financial manipulations, including fixing the stock prices of the company that owns BMW Motors and rigging poll results to favor candidates in her husband’s People Power Party. Investigators have raided the party headquarters in search of evidence to support charges against both Ms. Kim and her husband.

The former first couple are not reported to have been in touch with one another from their separate prison cells, but Mr. Yoon has made headlines for refusing interrogation by removing his prison garb, stripping to his underwear, and lying on the floor when investigators came to take him to court. They eventually left, promising to haul him into court later.

Ms. Kim, noted for her beauty as a former hostess in a high-priced club, has not yet resorted to stripping in order to avoid questioning.