Like convenience stores, many nationwide restaurant chains used to stay open 24 hours a day, targeting younger generations who want to dine or sip beer in the late-night hours.

But amid a decline in the number of nighttime customers, many operators are starting to close around midnight. And as cases of karoshi, or death from overwork, continue to make headlines, closing early is seen as a way to prevent long working hours at such establishments to ensure a better working environment.

Last week, Skylark Co., the operator of restaurant chains including Gusto, Jonathan's and Bamiyan, said about 80 percent of all its 987 eateries that currently operate around the clock will be closed between 2 a.m. and 7 a.m. starting in April.