Kazufumi Yamamoto is having such a hard time finding waiters and sushi chefs to fill jobs at Ganko Food Service Co. that he's going to boost wages for the first time in more than a decade.

"Positions remain open for several months, leaving some restaurants heavily understaffed," said Yamamoto, personnel head at the sushi-chain operator in Osaka. "The labor shortage has worsened to the point we have no choice but to increase pay."

The troubles facing Yamamoto, 43, reflect the pressures of a labor force that's shrinking, with just nine high school graduates on the hunt for a private-sector job now for every 10 just five years ago. Smaller companies reliant on part-time workers are bearing the brunt, pressuring them into wage gains that have yet to be reflected in the broader job market.