Lee says the 15-year-old fights her attempts to get him to log off, screaming and physically lashing out at her entreaties. She pulls up her sleeves to reveal bruises she says come from his blows.
Her son is among some 2 million people classified by the government as "Internet addicts" in South Korea, a nation of 49 million considered one of the most technologically wired in the world.
Some are becoming increasingly violent. Last month, a couple let their 3-month-old starve while they raised a virtual child in an online game, spending most of their days at an Internet cafe instead of caring for their newborn, police said.
The baby looked like "a mummy" because she had not been fed for so long, according to a Suwon police officer who investigated the case. He asked that his name not be used because the investigation was still under way.
In February, a 22-year-old bludgeoned his mother to death for "nagging" him about playing Internet games, police said. He then played games online for hours, paying with his mother's credit card, a police statement said.
Such incidents have alarmed the country, with the public calling for better measures against gaming addictions. The government announced last month it would take action by restricting access to popular online games, and is sending counselors to elementary schools to teach children about healthy Internet usage.
"It's a little ironic that what was invented to make our lives better has come to make it worse for some," said Park Hye-kyung, director of the I Will Center, a government-funded counseling center created in December to focus on the growing issue of Internet addiction.
"Internet addiction" may not be recognized as a medical condition or psychiatric disorder, but it often serves as a symptom of more serious underlying mental disorders such as attention deficit disorder and depression, said Dr. Kim Tae-hoon, a psychiatrist who treats teenagers.
Kim said the Internet is almost too readily available in South Korea. More than 90 percent of homes have broadband Internet access, according to the Organization for Economic Cooperation and Development. In addition to widespread broadband, Internet cafes known as "PC rooms" are open 24 hours throughout the country.
"In South Korea it's easier for citizens to play online games than to invest in their offline personal relations through face-to-face conversations," he added. "People are becoming growingly numb to human interaction."
Three out of 10 adults and some 26 percent of teenagers are addicted gamers, according to Eo Gee-jun, president of the Korea Computer Life Institute.
"Children start to play Internet games when they become fourth- or fifth-graders," Eo told The Korea Times newspaper last month. "They tend to be more attached to them as they grow up."
The Culture Ministry announced a joint project with major South Korean gaming companies earlier this month to implement a "late-night shutdown" on Internet games popular among young users. Access to three games will be blocked from midnight until 8 a.m. to users under age 18 when the program goes into effect later this year.
The ministry urged top game providers to monitor users by their national ID numbers, which include their ages, and to allow parents to check whether their children are using their IDs to play after hours.
And starting next year, gamers will be able to install free programs onto their computers that limit their access to the Internet, the government said last month.
"Government policies are important but it's also crucial for the public to take charge as well," said Lee Young-ah, an official at the Ministry of Culture, Sports and Tourism. "We want to alert as many people as possible on the seriousness of Internet addiction so that individuals can start monitoring themselves."
Nexon, a major South Korean gaming company, says the curfew is a first step in the battle against Internet addiction.
"We want to create a healthy culture of enjoying our games and not suffering from them as an illness," said Nexon spokesman Lee Young-ho.
The government has earmarked 10 billion won ($9 million) to educate the public about the dangers of Internet addiction and to fund counseling centers for the web-obsessed.
Park, the director of the I Will Center, warned precocious school-age gamers will find a way to get their fix.
"Clever kids know how to work their way around any hurdles to gaming, and I am sure they can quickly find a way to get around this one as well," she said. Her counselors visit elementary schools to teach children about safe Internet usage in hopes of preventing Internet addiction early on.
Lee Mi-hwa says she is counting the days until the curfew goes into effect in the fall.
She said her son stays up most nights posing online as "Julian," a handsome, dragon-slaying superstar who saves his beautiful princess girlfriend from fire-spitting monsters.
By day, he's sullen and unresponsive, flunking his classes and unable to communicate with his family except with screams and blows, she said as her son sat nearby, immersed in his computer game.
Lee says she's desperate for any measure that might bring her son out of his Internet bubble.
"I'm hoping that this new curfew will be (his) saving grace," she said, wiping away tears with her sleeve.