Many women quit professional-level jobs when starting families, only to find it extremely difficult to return to similar work later on. Through staffing companies, however, opportunities are expanding — albeit as part-timers — as small and midsize firms hire such mothers for their expertise.

"Here I get to do interesting work involving management. It's almost the ideal job," said 45-year-old Masako Tanaka, who works three days a week from 10 a.m. to 4 p.m. at Tokyo-based IT venture Whiteplus Inc.

Tanaka's previous job was also in the information technology industry. When she first returned to work after her daughter, now 7, was born, she landed a managerial position and was in charge of operations and project planning for mobile phone websites.