He says it is hard work but nothing like the pressures of his old job at a trading company.
"When I joined the company, I could only use like five days of holiday a year because the culture was like that," he says. "If the new guy asked for holiday more than five days, it's like other people think he is crazy or he doesn't care about the bosses."
Lee says that need to please superiors is part of the reason his colleagues would pull late nights, even if they were not actually busy.
"They just sit in their chair and they just watch their team leaders, and they're thinking, 'What time is he going to leave the office?'"
That could go some way to explaining why South Korea's productivity rate remains relatively low, even though South Koreans work some of the longest hours in the OECD -- an average of 2,057 hours per worker in 2014.
For comparison, the United States falls outside the top 10 countries. There, employees worked an average of 1,789 hours each during 2014.
Workers take complaints online
In recent years, the South Korean government has been discussing ways to improve workers' lives by limiting the number of hours that can be worked each week by law.
However, excessive overtime continues to be the most common complaint on the employment forum, Jobplanet.
Co-CEO Daniel Hwang says workers are venting online what they cannot say out loud.
"They don't actually stand up to their bosses. The culture is too polite to do that," Hwang says. "So we thought, you know, this platform might not work. But as soon as we launched, people had so many things to say in their minds and they're spilling out into our platform."
Hwang believes many South Korean men develop a hierarchical view of society during their military training, then bring that into the workplace.
So they feel they can never say no to the boss.
That extends beyond the office, and long past the time people would ordinarily be clocking off, into bars like the one Lee runs.
"If the team leader likes drinking or loves drinking, then their team staff usually have to join him for drinks," Lee says. "Even if there's no reason."
And you don't need a bartender to tell you that nothing puts a dent in productivity like a hangover.