South Korean President Yoon Suk Yeol speaks during an inaugural dinner at a hotel in Seoul, South Korea, Tuesday, May 10, 2022. AP
The inaugural ceremony was held in the National Assembly plaza, attended by over 40,000 ordinary people as well as dignitaries.
Yoon started his career as a public prosecutor at the age of 35, after failing to pass a bar exam for nine years.
Yoon gained fame and went from strength to strength with his investigation into political heavyweights and business tycoons.
He apprehended close aides to former President Roh Moo-hyun for violating the political fund law, a brother of former President Lee Myung-bak for breaching the political fund law, and Chung Mong-koo, former chairman of the country's second-largest family-run conglomerate Hyundai Motor Group, in a slush fund case.
Yoon was demoted in 2013 when he led a special investigation team to probe into the involvement of the National Intelligence Service (NIS), the country's spy agency, in the public opinion manipulation scandal.
"I love the prosecution office. I have no loyalty to any person," Yoon left his well-known words during a parliamentary inspection in 2013, acquiring a nickname of "sturdy prosecutor" from local media and a full support from lawmakers of the then main liberal opposition Democratic Party.
Yoon secured an opportunity to restore his fame in late 2016. He became the head of the investigation team of an independent counsel, who looked into the influence-peddling scandal involving President Park Geun-hye and her confidante Choi Soon-sil. It led to the impeachment of Park in March 2017.
In May 2017, the newly-elected President Moon Jae-in named Yoon as chief of the Seoul Central District Prosecutor's Office, enabling Yoon to come back to one of the highest prosecution positions in a dazzling way.
Yoon's office reinvestigated the NIS public opinion manipulation case, finding out the involvement of the police and even the defense ministry.
His office also arrested former President Lee Myung-bak for bribery and Yang Sung-tae, former chief justice of the Supreme Court, for abuse of power.
The liberal Democratic Party supporters extolled Yoon as a hero who saved the country, while conservatives vilified him as a traitor who destroyed the conservative bloc. The public sentiment was completely overturned before long.
President Moon appointed Yoon as prosecutor general in July 2019, ordering Yoon to strictly investigate corruptions even relevant to the incumbent government. It was the unprecedentedly fast promotion, leading to the resignation of several high-ranking prosecutors.
Shortly after the appointment, Yoon started a probe into the family of Justice Minister Cho Kuk, one of close aides to President Moon and former senior presidential secretary for civil affairs, over a series of controversies that include the alleged forgery of academic achievements of his daughter.
Tens of prosecutors and investigators reportedly raided about 100 locations, including Cho's home, provoking harsh criticism from the Democratic Party supporters, hundreds of thousands of whom held candlelight rallies on a main road beside the building of Yoon's office and demanded his resignation as prosecutor general.
Conservatives welcomed the investigation, delivering garlands and wreath trees with a written message of support for Yoon that were lined along his office.
Amid the growing calls from the liberal bloc to resign and the rising support from conservative voters, Yoon stepped down as prosecutor general in March 2021 and declared his candidacy for president in June of the year.
He officially joined the People Power Party a month later.