[1] During the early 21st century, Sung led the South Korean anti-feminist movement opposing female-preferential policies.

In early adulthood he was a businessman, and in October 1999 he participated in the movement opposing the abolition of preferential treatment for discharged soldiers.

From 1999 until his death Sung argued for the restoration of the Korean Army bonus points system (군가산점 제도).

[2] In 2011, he began offering assistance and counseling to battered husbands, househusbands, teenage runaways and male and child victims of violent crime.

Sung opened a shelter for homeless persons, male victims of violent crime, teenage runaways and gay and transgender people.

[6] At that time Sung became conscious of authority, developed a loathing for the patriarchal system and complained that South Korean society treated males cruelly.

In 1987, Sung joined the South Korean Army and served with the 3rd Infantry Division (육군 제3보병사단 陸軍第三步兵師團) in Cheolwon (Gangwon Province)[6] until 1990.

[9] From August 26 to November 30 of that year, Sung worked for the Thomas McFly Consulting and Headhunting Company (토마스 맥플라이 컨설팅 & 헤드헌팅사) in the Eastern District of Daegu before resigning to continue his human-rights campaigns.

[10] Sung campaigned for the abolition of the Ministry of Gender Equality and Family in the 2002 and 2007 presidential elections, questioning its justification.

[12] In August 1994 Sung married Park Eun-kyong, an internist and professor at the College of Medicine of Chung-ang University.

In 1999 Sung opposed abolishing the South Korean military's bonus-points system (군 가산점;軍 加算點)[13] and military veterans' compensation, and supported the abolition of the South Korean female quota (여성 할당제;女性割當制) and female employment quota systems (여성고용할당제;女性雇傭割當制).

Sung advocated the resurrection of the South Korean military bonus-points system and the abolition of female quotas until his death.

"[14] He argued that the totalitarianism of a few female chauvinists excessively suppressed male sexuality, the arts, pop culture and freedom of expression and thought.

Comparing South Korean government policies to prohibition in the United States, Sung said that restricting pornography had undesirable side effects and labeled normal men as sex offenders.

From August 1999 to 2001, Sung advocated the protection of the South Korean military's bonus-points system and had a small number of sympathizers.

Feeling that the system had symbolic meaning for fathers and families, he argued with South Korean radical feminists on the Internet.

On December 12, 2012, Sung told presidential candidate Park Geun-hye that to "recover lost fathers' rights is the way for my family's happiness".

Sung encouraged the recognition of homophobia, emphasizing that sexuality is personal,[21] and provided accommodations and job placement for homeless, unemployed young male runaways and gay and transgender people.

hosted by Choi Min-hee of the Democratic United Party at the National Assembly building in Yeouido, Seoul,[26] Sung said: "Who are those crazy beings who oppose the protection of children and teens against sex crimes?

"[26] According to Sung, "Just 20 years ago, women would go to the pharmacy and hide their sanitary pads in newspaper and buy them as if they were drugs.

But 20 years later, Korean women’s sanitary pads are in your face, and they even have a menstruation festival ... Had men not acknowledged and understood femininity, do you think this would have been possible?

[28] Opponents said that Sung's work to support the rights of men was misplaced because South Korea is a male-dominated society.

[34] Sung criticized South Korean menstrual leave as sexist, arguing that it was unnecessary for most women since it protected motherhood.

Sung jumped from the Mapo Bridge into the Han River, leaving a note saying that he would risk his life to raise ₩100 million (about $94,000) in donations to pay debts owed by Man of Korea.

[39] Sung later said that he did not intend to commit suicide, but wanted to draw attention to his group; he would jump, whether or not he received the money.

"[41] He left a note: Dear citizens, ever since the mid-1980s when gender-equality issues came into public awareness, our country has been focusing on overhauling laws, policies and social systems to improve women’s rights and status.

[42]On July 26, 2013, Sung took a taxi from Yeongdeungpo to Mapo District with Han Seung-oh, Lee Ji-hun and five other people.

[38][44] About 50 firefighters from the Yeongdeungpo Fire Station, one helicopter and three rescue boats continued the search Saturday and Sunday; six ambulances stood by.

[12] Sung's body was found near the south end of the Seogang Bridge, connecting Yeouido to northern Seoul, on July 29.

[45] On August 1, Sung was cremated and his ashes buried in a crypt in the Gyongsan Park Cemetery (경산 공원 묘원) in Namchon (남천면), Gyeongsan, North Gyeongsang.