By Agence France-Presse
Since May, the monthly demonstration in Seoul has shattered records to become the biggest-ever women's protest in South Korea where the global #MeToo movement has unleashed an unprecedented wave of female-led activism.
The target of their fury: so-called "molka" or spycam videos which largely involve men secretly filming women in schools, offices, trains, toilets and changing rooms and which are so prevalent they make headlines on a daily basis.
"Entering a public bathroom is such an unnerving experience these days," Lee said, adding that she always looked around the walls to see if there were any "suspicious holes".
"You never know if there's a spycam lens hidden inside... filming you while you pee," the 21-year-old student told AFP, saying she sometimes stabbed the holes with a pen to shatter any secret lenses, or stuffed tissues inside them.
The statistics are startling, with the number of spycam crimes reported to police surging from around 1,100 in 2010 to more than 6,500 last year.
The offenders have included school teachers, professors, doctors, church pastors, government officials, police officers and even a court judge.
In some cases, the victims' own boyfriends or relatives were responsible for the crimes, in a troubling reflection of South Korea's deep-rooted patriarchal norms.
Fed up of living in fear, women are fighting back.
More than 55,000 attended last month's protest in Seoul, according to its organisers, although police put the attendance at around 20,000.
"The pent-up anger among women has finally reached a boiling point", one of the protest organisers who only identified herself as Ellin told AFP.
Asia's fourth-largest economy takes pride in its tech prowess, from ultra-fast Internet to cutting-edge smartphones.
This picture taken on June 9, 2018 shows a red placard reading "My life is not your porn" during a monthly protest by South Korean women against secretly-filmed spycam pornography in Seoul. // AFP PHOTO
But these advances have also given rise to an army of tech-savvy peeping Toms, with videos widely shared in internet chatrooms and on file-sharing sites, or used as adverts for websites promoting prostitution.
Although all manufacturers of smartphones sold in the South are required to ensure their devices make a loud shutter noise when taking photos -- a move designed to curb covert filming -- many offenders use special apps that mute the sound, or turn to high-tech spy cameras hidden inside eye glasses, lighters, watches, car keys and even neckties.
A 43-year-old man was arrested last month for secretly filming occupants of Seoul motels for four years, installing ultra-mini lenses inside TV speakers and other equipment after posing as a guest.
A police raid uncovered more than 20,000 spycam videos at his home.
In June a 34-year-old man was arrested for secretly filming women inside toilets and selling thousands of videos online for up to 100,000 won ($90) apiece.
Justice is rarely served -- most offenders are fined or given suspended jail terms, which many women's rights groups decry as a mere slap on the wrist.
Except, campaigners say, in the rare cases where the perpetrator is female and the victim male.
The arrest in May of a woman who secretly filmed a male model posing nude at a Seoul art college, days after she shared the image online, was a catalyst for the unprecedented protests this summer.
"The police have rarely responded when countless female victims asked for the immediate arrest of the offender", Seo Seung-hui, head of the non-profit Korea Cyber Sexual Violence Response Centre, told AFP.
In this case the suspect was paraded in front of TV cameras while police raided her home to search for evidence. Authorities even launched a probe targeting those who shamed the male model online in an uncharacteristically swift response.
"The women saw how quickly...the police responded to this rare case in which the victim was a man...such unfair treatment fuelled the recent wave of anger", Seo said.
'Make change happen'
Campaigners have called for harsher punishments for those who film, distribute and view such images. They have also urged tougher regulations to restrict the sale of high-tech spycam equipment.
This picture taken on June 9, 2018 shows a South Korean woman holding a red placard reading "Angry women will change the world" during a monthly protest against secretly-filmed spycam pornography in Seoul. // AFP PHOTO
But in a sign of the ugly fight ahead of them, many of the protesters at a recent rally kept their faces covered and declined to be photographed due to worries over personal safety, with previous participants becoming the targets of relentless online bullying.
Despite their fears, they refuse to back down.
"Seeing so many women gather together to speak up was a deeply empowering experience", protest organiser Ellin said.
"We have power. Together, we can make change happen", she said.