The balance of shares bought on credit hit a nine-month high last week, mirroring a leap in investor sentiment.
The outstanding balance of long margin positions stood at 1.38 trillion yen, up 86.51 billion yen from a week earlier, according to a weekly industry report.
The balance rose for the second week in a row to hit its highest level since Sept. 7, just days before the Sept. 11 terrorist attacks in the U.S. sent stocks and bonds reeling across the globe.
Individual investors and brokerage dealers geared up for increased purchases of shares on credit last week, banking on an anticipated economic recovery.
Forthcoming official figures for the first quarter are now widely expected to offer fresh evidence of a strong economic pickup in Japan.
There is continuing speculation that Japanese economic growth has by far outperformed U.S. growth in recent months.
Shares showing lopsidedly high balances of long margin positions included construction and other long-neglected issues.
Among these were Haseko, Penta-Ocean Construction, Nippon Light Metal and Toshiba.
The balance of shares sold short, on the other hand, turned lower for the first time in four weeks.
The balance of short margin positions stood at 1.05 trillion yen, down 42.61 billion yen.
Shares showing high balances of short selling included Nippon Steel, Mitsubishi Electric and Marui.
Short sellers unwound their positions, benefiting from the recent bear market.
The benchmark 225-issue Nikkei average ended the week at 11,763.70, down 212.58 points, or 1.8 percent, on the week.