In late August 2021, a 56-year-old male named Kang Yoon-seong, who had a history of robbery and sexual crimes, committed a series of murders against two victims in the Songpa-gu district of Seoul, South Korea. Afterward, he turned himself in to the police. On August 26th, around 5:00 PM, Kang Yoon-seong purchased a kitchen knife from a mart in Samjeon-dong, Songpa-gu. Prior to that, at 3:57 PM, he bought a cutting machine from a hardware store in Ogum-dong. Between 9:30 PM and 10:00 PM on August 26th, Kang Yoon-seong suffocated and killed a woman in her 40s whom he had met at a karaoke establishment, using a blanket. He claimed that he killed her because she refused to engage in sexual intercourse. The body of this woman was not discovered until Kang turned himself in. The police had visited Kang's residence five times, including on the day he damaged his electronic ankle monitor, from 6:00 PM on the 27th to 2:00 AM on the 28th, but they did not uncover the first murder. A police

  On December 10, 2021, in a villa located in Jamsil-dong, Songpa-gu, Seoul, a murder took place where Lee Seok-jun (then 25 years old, born in 1996) killed A's (then 21 years old, born in 2000) mother, who was a former lover, and injured A's younger brother. On December 5, Lee Seok-jun sexually assaulted A after taking her mobile phone at his house in Cheonan, and recorded the act with his own phone. On December 6, A reported the suspect for sexual assault, and from December 7, she was under police protection as a victim and received a smartwatch. On December 10, around 2:30 PM, Lee Seok-jun broke into A's house, who was his ex-girlfriend, and attacked A's mother (then 49 years old, born in 1972) and younger brother (then 13 years old, born in 2008) with a weapon. A's father, who was out at the time, became aware of the incident during a phone call with the mother and reported it, but they had already been injured by the weapon. The mother was transported to the ho