[8] Yoon Suk-yeol, who had clashed with the Moon administration and Democratic Party,[9] publicly opposed the idea of separating powers of investigation and prosecution.

[10] Minister of Justice Park Beom-kye said he will gather various opinions from members of the prosecution on establishing an agency that would handle serious crimes.

[15] On the other hand, leader of the Democratic Party Lee Nak-yon has criticized Yoon, saying his resignation "out of the blue" was absurd for a public official.

[16] Public support for Yoon Suk-yeol rose sharply to take the lead over other potential presidential candidates in South Korea.

[21][22] Seo Jung-hyup (acting) Independent Oh Se-hoon People Power The death of Park Won-soon, the mayor of the largest city in South Korea, was hugely impactful on the 2021 by-elections.

[25] So, it was seen as a shock that the person who had been fighting for women rights committed suicide after his female employee accused him of sexual harassment.

[27] In December 2020, the majority of the potential candidates in Seoul are women, showing the rival parties' bid to promote themselves as women-friendly.

[28] Three women (Na Kyung-won, Cho Eun-hee and Lee Hye-hoon) from the main opposition People Power Party have announced their Seoul mayoral bids.

The possible female candidates from the Democratic side are Minister of SMEs and Startups Park Young-sun and Anti-Corruption and Civil Rights Commission Chairwoman Jeon Hyun-hee.

Then, Independent frontline runner Ahn Cheol-soo who had been a strong supporter of Park Won-soon's famous civic group endorsed him for Seoul Mayor.

[33][34] Thanks to the support of Ahn Cheol-soo, Park Won-soon overtaken Na Kyung-won, the frontline runner of the ruling Grand National Party, in a poll.

[40] Because of first past the post voting, South Korean politicians often try 'candidate unification' by opinion polls not to split the voters of their side.

[47] On 17 March 2021, Park Young-sun defeated Open Democratic Party candidate Kim Jin-ae in 2nd round of unification primary.

"[51] Keum criticized Ahn's remarks in a radio interview the following day, saying he was disappointed as they lacked consideration for the basic human rights of the LGBTQ community.

[58][59] On 23 March, both campaigns jointly announced Oh Se-hoon's victory from two mobile surveys of a total 3,200 Seoul residents that evaluated the candidates' adequacy and competitiveness.

[5] Ahn Cheol-soo said he accepts the outcome, before vowing to work hard to help the unified opposition bloc win the election.

[63] Moreover, since Seoul and Busan are the first and second cities in South Korea by population, one of the biggest concerns of the Democratic Party is that this by-election which will be unfavorable to them may affect the 2022 presidential election.

[3] On 1 March 2021, Former Minister of SMEs and Startups Park Young-sun won the primary and become the Democratic Party nominee in 2021 Seoul mayoral by-election, defeating Assemblyman Woo Sang-ho.

[69] On February 3, 2021, Justice Party decided not to field candidates in the April mayoral by-elections after its leader was expelled for a sexual abuse scandal.

[79] During the first televised debate, both candidate clashed with real estate issues and Moon Jae-in administration's anti-speculative policies amid LH scandal.

Park Young-sun raised allegations against Oh Se-hoon that he received 3.65 billion KRW in 2009 in compensation for land in Seoul's Seocho district, after his involvement in the area being designated a residential zone.

Park Young-sun argued during the debate that he lied about the controversial land development project, which allegedly benefited his wife and her family.

Then, Oh said Park's candidacy itself is a lie by the ruling party, which had promised not to produce a candidate for a by-election made necessary due to its elected members' indiscretion while in office.

[94] Young voters, who have traditionally sided with the Democratic Party, voted for the conservative PPP according to the Seoul exit polls.

More importantly, the Democratic Party's continued support for feminism and women-prioritized policies had caused severe social divisions between young men and women, which prompted male 20s to vote for the conservative Oh.

In contrast, Oh embraced the youth vote by hosting campaign events with young voters making endorsement speeches went viral online, and by promising to deliver speedy measures to increase housing supply in Seoul and also to look after the reinstatement and recovery of the victim of sexual harassment by the previous mayor Park Won-soon.