North Korea’s charm offensive at the Olympics has made headlines, but not everyone in Seoul is delighted by the synchronised cheerleading squads or the enigmatic smile of dictator Kim Jong-un’s sister.

For Seoul resident Hwang In-cheol, 50, the North’s presence at the Winter Games reminds him of his father, who has been held captive in North Korea since 1969.

Hwang and other human rights activists argue South Korea’s promotion of the Games in Pyeongchang as the “Peace Olympics” overlooks the forced abduction and detention of its citizens.

“The South Korean government has a legal obligation to urge North Korea to return my father,” Hwang said. “But instead of doing that, the government is keeping its silence, and has become an inadvertent accomplice to these criminal acts.”

The UN estimates up to 100,000 South Koreans were captured and held in North Korea during the 1950-1953 war, and another 516 have been abducted since, most fishermen.

Hwang’s story began when he was two. On December 11, 1969, his father Hwang Won boarded a Korean Air Lines flight for a short journey to Seoul from Gangneung, the city now hosting Winter Games events.

Ten minutes after take-off, a hijacker forced the plane to land at Yonpo Airfield, near the city of Hamhung in North Korea.

A standoff ensued for two months, with North Korea initially insisting the pilot had flown to the country on his own. But after international pressure and massive street protests in South Korea, North Korea released 39 of the 50 South Koreans on the flight. Seven passengers, including Hwang’s father, a television producer, and the four crew members were kept behind.

North Korea still insists those 11 chose to stay there.

For Hwang, it was the start of a childhood waiting for his father, then 32, to come home. His mother told the distraught toddler that his father had gone to America and would be returning for Christmas.

“When I was with my friends, I said, ‘My father’s returning this Christmas with toys’,” Hwang said. He recalls seeing a cowboy cartoon: “I told friends that when my father returns, he’ll be bringing a horse.”

In 2001, Hwang began actively working on his father’s case. North and South Korea had just started a limited series of family reunions for separated families. Hwang was watching a story on the news about the reunions that showed one of the abducted flight attendants meeting her mother. He looked at his own daughter, then two years old, and “felt the pain of a parent being ripped away from their children”.

Hwang decided to start a campaign for his father’s release. He registered with the Korean Red Cross, which facilitates the family reunions. But the North Korean side insisted his father’s whereabouts could not be confirmed.

Hwang turned to South Korea’s Ministry of Unification, which manages inter-Korean affairs, without success. Hwang argues cases like his have long been ignored to improve relations between the two Koreas.

“As the North and South attempt more rapprochement, more peace initiatives, issues like ours become a hindrance,” he said. “The South Korean government wants the families of the victims to remain quiet.”

Hwang didn’t give up. He turned to the UN which highlighted his father’s story in a 2016 report on separated families.

“These violations are not going unnoticed by the international community,” said Signe Poulsen, the South Korea representative with the UN Office of the High Commissioner for Human Rights.“Resolving these abductions becomes a crucial and central tenet of any sustainable future peace.”

Hwang still believes he’ll see his father again. A broker who helps North Korean refugees escape told Hwang recently that his father, now 80, is still alive and living in the city of Pyongsong.

Hwang started a Bring My Father Home campaign last year with the help of a local charity, and supporters held a panel discussion at South Korea’s National Assembly.

Some of the speakers criticised the friendly images of North Korea at the Olympics, while Hwang’s father and others were still being held.

“The South Korean government has spent a huge amount of tax money to provide the venue for North Korea to spread its propaganda,” said Kim Seok-woo, the South’s former vice minister of unification. “It is truly worrisome. I fear we are giving North Korea nothing more than the time it needs to develop its nuclear arsenal.”

Seoul should have two diplomatic objectives in dealing with North Korea: denuclearisation and improvement of human rights, said Lee Jung-hoon, a professor at Yonsei University’s Graduate School of International Studies. “The abduction incident of Korean Air is an important part,” he said. “We need to clearly convey these objectives. Otherwise the South Korean government will not have a firm authority backed by public support,” he said.

Hwang said watching coverage of the North’s delegation at the Olympics made him uneasy. He said: “I keep wondering how South Korea will be used by North Korea next.”