SEOUL, South Korea — In 1973, a newspaper advertisement in the South Korean city of Daejeon announced the arrival of “The Messenger From the Spiritual World,” a messiah who embodied the best of Buddhism, Christianity and other religions.
“Religious leaders of all beliefs, come and learn from him!” it read. “Those in distress or afflicted with incurable diseases, come and seek his counsel!”
The Messenger was Won Ja-kyong, one of several aliases used by Choi Tae-min — a man who, more than 20 years after his death, is at the root of a scandal that has roiled this country and sent PresidentPark Geun-hye’s approval rating to the lowest point of any modern South Korean leader, according to Gallup Korea. Tens of thousands of people marched in Seoul, the capital, on Saturday, demanding Ms. Park’s resignation.
The scandal’s primary figure is not Mr. Choi but his daughter, Choi Soon-sil, who has inherited his role as a secretive adviser for the president. This past week, Ms. Choi was arrested and charged with using her influence with Ms. Park to extort large sums from Korean companies.
Ms. Park has admitted letting Ms. Choi, who has no government job or background in policy, edit some of her speeches, and a cascade of news reports have alleged that Ms. Choi had considerable sway in the presidential Blue House and other government agencies.
But what infuriates many South Koreans about the Choi affair is not merely that Ms. Park had a secret adviser, or even the possibility that the adviser turned a profit from the relationship. It is the notion that their president has been in thrall for decades to a family of religious charlatans — a shameful throwback, in their view, to ancient stories of Korean kings and queens brought to ruin by deceitful monks or fortunetelling shamans.
“I am so embarrassed that if a foreigner asks me where I am from, I feel like saying I am Chinese or Japanese,” Oh Yoo-jeong said at a recent antigovernment rally in Seoul. “Until now, I had thought this kind of thing happened only in historical dramas on TV.”
Hand-held signs at demonstrations have read, “I’m ashamed to call this our country!”
There is no evidence that Ms. Choi has continued the colorful religious practices of her father — the founder of an obscure sect called the Church of Eternal Life — or that Ms. Park, who befriended both Chois in the 1970s, was ever his spiritual follower. Still, in protest rallies, on social media and even in newspaper editorials, Ms. Park is depicted as a puppet, manipulated while a young woman by Mr. Choi and while president by his daughter.
Rumors to that effect are rampant. After a cable news channel discovered that Ms. Choi had advised Ms. Park on what color to wear during an overseas trip, some suggested that she had based her choices on an astrological system. Others have raised the possibility that Ms. Choi inserted mystic symbolism into decorations at Ms. Park’s inauguration ceremony in 2013. Some people have gone so far as to call Ms. Choi a “sorcerer regent.”
The ties between Ms. Park and the Chois, which have been a matter of public record for decades, have long generated gossip of that kind, but it was never taken seriously by large numbers of people until the recent revelations of Ms. Choi’s influence in the Blue House.
Her father’s activities in the 1970s, around the time he met Ms. Park, were described in journals by Tak Myeong-hwan, a researcher into fringe religious figures. He describes visiting the “Messenger” known as Won Ja-kyong in 1973, and watching him and his followers chant incantations in front of brightly colored circles drawn on a wall. Shamans, the practitioners of traditional spiritual rituals who still thrive in Korea, came to see him and cowered before him, Mr. Tak wrote.
When the two met again in 1975, the Messenger drove a Jeep, had a different name — Choi Tae-min — and called himself a Christian pastor, leading a group he called Crusaders to Save the Nation. According to Mr. Tak, Mr. Choi said he worked for “the esteemed daughter Geun-hye” and had free access to the Blue House.
South Korea was then led by the dictator Park Chung-hee, the father of Ms. Park, whom Mr. Choi had befriended. In 1975, according to a report written by South Korea’s intelligence agency, Mr. Choi had written to Ms. Park asking to meet her, saying he had communicated with her mother, who was killed by a pro-North Korean assassin the previous year. (Ms. Park and Mr. Choi later denied that he had made such a claim.)
Though Park Chung-hee would prove skeptical of Mr. Choi, the Crusaders to Save the Nation were an idea the unpopular Cold War dictator could hardly refuse: pro-government pastors, organized in a crusade against Communism. Members donned officers’ uniforms and underwent military-style training.
Newspaper articles from the time say Ms. Park attended the group’s inaugural ceremony and was made its honorary president. Government television footage from the time shows Ms. Park, escorted by a young Choi Soon-sil, attending a gathering of volunteers and receiving adulation reminiscent of the personality cult surrounding the Kim family in North Korea.
After Park Chung-hee was assassinated in 1979, Ms. Park retreated into seclusion, and Mr. Choi remained a trusted confidant in the years that followed, according to a 1989 government intelligence report that was recently obtained by the Chosun Ilbo newspaper. The report said he had provided her with daily necessities and predicted that she would one day be a “queen.”
It also said he had embezzled funds from a foundation run by Ms. Park. An earlier intelligence report had accused Mr. Choi of using his ties with Ms. Park to extort money from businesses, a charge echoed in the current allegations against his daughter.
In 1990, Ms. Park’s sister and brother wrote to President Roh Tae-woo, asking him to stop what they called Mr. Choi’s continuing extortion and to rescue their sister from what they called his manipulation. (Ms. Park later called such accusations “slander.”) on Friday, Ms. Park acknowledged that she had cut ties with her siblings since becoming president to prevent influence-peddling by relatives.
After Mr. Choi died in 1994, his daughter appears to have taken a prominent role in Ms. Park’s life. When Jeon Yeo-ok, a former television journalist, met the two in the mid-1990s, she said, they were “just like a princess and her lady in waiting.”
Today, there is no sign of the religious sect Mr. Choi once operated, and Ms. Park and the Chois have denied practicing cultlike or shamanistic rituals. But Ms. Choi’s scandal has revived old rumors about her father, which in turn have reinforced speculation about Ms. Choi, in whom many people purport to see a new version of him.
Korea, a land frequently torn by wars and deprivations, has been a rich ground for fringe religious groups. When the ferry Sewol sank in 2014, killing more than 300 people, South Koreans were shocked to learn that the ship belonged to a cult leader.
Shamanism remains a strong force in the country, despite past governments’ attempts to discourage it. Thousands of its practitioners, known as mudang, still operate, almost all of them women who claim to be able to communicate with the dead. Most of their clients are also women.
Because of this, when Ms. Choi is called a shaman — as she often is — some sense a faint misogyny at play. Some conservative politicians have criticized Ms. Park for entrusting state affairs to a mere “ajumma,” or housewife. Men joke that the scandal has dimmed the chances of South Korea’s having another female president.
“President Park and Ms. Choi made female leadership a matter of ridicule,” wrote Yang Sun-hee, a female editorial writer at the JoongAng Ilbo newspaper.
Even amid the anger over the Choi scandal, many are taking delight in it. After Ms. Choi lost a shoe during a media scrum this past week, the resulting headline was “The Shaman Wears Prada.” A running joke is that Ms. Park can do nothing without asking “Soon Siri,” a play on Ms. Choi’s name and the iPhone voice-command function.
Bloggers have also labeled her Soonderella, a mix of her name and Cinderella. But as the protests continue, the story seems unlikely to have a Cinderella ending.
“From now on,” Ms. Park said on Friday, “I will completely cut off any private relationships in my life.”