A mass assault on a Mongolian immigrant middle school girl in Yangsan, Korea, in 2021

 On July 3, 2021, four middle school students assaulted a female student who is a Mongolian immigrant in Yangsan City. They continued the assault for six hours and videotaped and disseminated the crime. 

A police investigation found that the assault not only lasted six hours from midnight to dawn, but also forced the victim to drink and force him to feed cigarette butts and wasabi after tying his hands and feet. In addition, the perpetrators threatened to retaliate when reporting, pressured them to cover the wounds caused by the assault, and verbally abused them.

In November 2022, prosecutors found that the perpetrators threatened police to lie that the victim had other injuries, and further crimes, including indecent assault, sexual exploitation, and video distribution, were committed.

The Yangsan Police Station sent two middle school students to the prosecution at the end of October on charges of joint assault under the Punishment of Violence Act, and the other two were transferred to the Ulsan District Court's juvenile department. However, the incident later became known, sparking controversy over the police's inadequate response.

Police visited the house where the incident occurred after receiving a report that the perpetrators and the victims were together. When there was a scuffle with the perpetrators, victim A's aunt reported it to the police. However, the dispatched police left the crime scene after checking only the main room, and the missing women and teenagers at the Yangsan Police Station, who received a runaway report, also did not find A hiding behind the veranda washing machine. After checking only the main room and bathroom, we decided that Ms. A was not there, so we withdrew. The problem is that victim A was hiding behind the veranda washing machine at the time.

Controversy has been raised that the police did not properly check the house because they judged it to be a simple runaway, and that they also did not check whether the house was a "house without guardians." In addition, although victim A's aunt submitted a statement containing the damage to the police, the police investigation of the victim took place on August 13, about a month and a half after the incident. The police only charged two of the four female middle school students with joint assault, the other two avoided punishment as juvenile offenders, and all charges of imprisonment, intimidation, and video distribution were excluded.

Police have apologized to the victim's family for this and say they will also investigate the leak of assault videos.

On December 6, 2021, a Korean resident was assaulted in Mongolia. As a result, Mongolian residents regard it as retaliation for the assault on a middle school girl in Yangsan. According to local residents, Mongolians are aware of the assault because state media and other broadcasters in Mongolia reported the incident, and after the incident, the atmosphere in Mongolia is not good, such as a protest call to the Mongolian consulate or a demonstration in front of the Korean embassy.

On December 16, 2021, the National Human Rights Commission of Korea launched an ex officio investigation into the assault on a middle school girl in Yangsan. The NHRC concluded that it is necessary to interview the victims and their families and investigate the police's actions, the progress of the investigation, and the details of the school and education office's case measures to investigate allegations of lack of protection. The National Human Rights Commission of Korea says it will consider ways to improve the victims if they are confirmed to have violated their human rights.

On November 2, 2022, prosecutors charged the perpetrators with additional charges of producing and distributing sexual exploitation. The four perpetrators will be sent to juvenile detention for a short period of time, and they can be imprisoned for up to six months.