The number of accounts opened at five major Japanese securities firms in January increased by over 900,000 from the previous month as the nation’s new tax-exempt retirement savings system bolstered demand.

SBI Securities, the largest online brokerage, saw the biggest number of account openings on record. They rose 274,000 on a net basis, while Rakuten Securities added approximately 280,000. Monex saw a significant increase of about 320,000, due in part to transfers from its partner Aeon Bank. Other securities companies also saw thousands of accounts opened.

Since January, government has ramped up the preferential treatment of the retirement accounts, known as Nippon Individual Savings Accounts or NISAs, as it aims to accelerate the flow of household financial assets from savings to investments. The net openings bring the total of accounts at the five brokerages to more than 28 million, about a fifth of Japan’s population.

The new NISAs are one of a slew of measures to lure more buyers to the Japanese market. That’s charging up the rally in stocks, with both major indexes trading near the highest levels in about 34 years.

At the same time, the record money flowing into overseas investments is fueling concerns that the weakness in the yen may persist, as signs the Bank of Japan isn’t likely to rush to raise rates keep the focus on higher-yielding assets abroad.