Takanori Sakai works the graveyard shift four nights a week at the FamilyMart store he owns in Himeji, Hyogo Prefecture, because he can't afford the higher pay employees demand these days.

"More and more stores can't secure a profit," the 57-year-old said. Problem is, with competition just down the street, raising prices to cover higher wages risks turning off customers who have become accustomed to steady prices for a generation.

Sakai and his fellow convenience-store owners are on the front lines of the battle with a "deflationary mindset," one compounded by a declining population. As the Bank of Japan repeatedly urges businesses to fatten paychecks to help stoke inflation, convenience-store chains are turning to automation and other means to absorb higher labor costs.