A week before her son died Park Mi-suk asked him to quit his job.

For more than a year, the 27-year-old had been working overnight shifts at a warehouse for the country’s largest online retailer, Coupang. He steered pallet movers with stacks of plastic bins and cardboard boxes across the sprawling space.

In that time, Park says, her son lost 15kg and often complained of how tired he was.

But Jang Deok-jun refused to quit. He compared his job to being on a seesaw: if he stepped down, his co-workers would struggle to keep going.

The following week, Park found him unconscious and hunched over in the bath.

“We pulled him out and performed first aid. We rushed him to hospital, where they declared him dead.”

Jang died of a heart attack. The state-run insurer that covers healthcare for workers, Comwel, blamed his death on overwork following an investigation.

Park wishes she had noticed Jang’s exhaustion sooner. “I didn’t pay attention to my son’s words, so I lost my son. But I hope others won’t repeat the same mistake.”