"It really is as if we are putting a minus against our names, causing problems for our colleagues by not being around to pull our weight," said Ogino, a 38-year-old father of two. "In spite of it all, I'm glad I did it."

With only 1 percent of the country's eligible male workers taking time out, dads like Ogino are hard to come by in Japan. Japan's fathers spend less time on child care and housework than their counterparts in any other developed country. But thanks to a new set of government initiatives that encourage working dads to take time off — part of a broader effort to boost Japan's rock-bottom birthrate — the number of fathers who swap their desks for diapers may be about to rise.

Under the revised Child-care and Family-care Leave Law, which takes effect on Wednesday, fathers will be allowed to take more time off to look after their children. Employers will also be obliged to allow a shorter six-hour working day to staff with children under three years old and in some cases, fathers will be exempt from working overtime. Masayuki Yamaguchi, a spokesman for Japan's labor ministry, said the initiative, which includes the launch of a self-help website, aims to help dads manage their work-life balance.

According to a Ministry survey, as many as a third of Japan's dads would like to take paternity leave. But many of Japan's "salarymen," who are notorious for working grueling hours, are afraid that taking time out as a stay-home dad could harm promotion prospects and damage relations with colleagues who have to cover for their absence. Even at the ministry, leave-taking dads account for a mere 2.3 percent, far below the government's target of 13 percent by 2020, Yamaguchi said.