The balance of shares bought on credit rose for the fourth straight week last week, reclaiming the 1.2 trillion yen level for the first time in five months.
The outstanding balance of long margin positions stood at 1.208 trillion yen at the end of the week, up 15.96 billion yen from a week before, according to industry figures.
The Tokyo stock market has shown a generally positive tone in recent weeks, prompting investors to move in.
Margin buyers opted for a wide range of low- and medium-priced cyclical issues that had long been neglected, banking on an economic recovery, brokers said.
Shares selected for margin buying most frequently by individual investors and brokerage dealers included Sumitomo Metal Mining, Nippon Light Metal and other nonferrous metal issues.
The balance of stocks sold short, on the other hand, fell for the fourth week in a row.
The balance of short selling stood at 952.33 billion yen, down 131.93 billion yen from a week before.
The short-sale balance slipped below the 1 trillion yen level for the first time in two months.
After having topped the 1 trillion yen level for the first time in 12 years in late October, short sellers have often gained the upper hand over margin buyers in recent months. This is no longer the case.
The balance of short selling has visibly declined since the government tightened controls on sales of borrowed shares in early March.
At the end of last week, the long-short ratio stood at 1.27, up from 1.09 a week earlier.