No one needs a lean-in movement like Japan's women.

I had this conversation in Tokyo 12 years ago with Sheryl Sandberg, long before she joined Facebook Inc. and wrote her book on female empowerment. We were listening to her boss at the time, U.S. Treasury Secretary Lawrence Summers, speak about the need for structural reforms to the Japanese economy, in a giant auditorium devoid of women. It was one of several male-dominated events that day. The author of "Lean In" leaned over and asked me half-seriously: "There ARE women in this country, right?"

A dozen years on, Japan's leaders appear to have realized that the two problems are intertwined: The lack of women in the workforce poses one of the biggest structural impediments to faster growth. Japan's institutionalized sexism deepens deflation, hurts competitiveness and exacerbates the demographic trends that make Japan's debt load so dangerous.