The balance of shares sold short topped 1 trillion yen for the first time in seven weeks last week, mirroring growing skepticism about the outlook for domestic stock markets.
The combined balance of short sales on the Tokyo, Osaka and Nagoya stock exchanges stood at 1.04 trillion yen at the end of the week, up 116.76 billion yen from a week earlier, according to a weekly industry report.
Short selling rose for the second week in a row.
Sumitomo Mitsui Banking Co. topped the list of shares showing marked rises in short selling. It was followed by Sumitomo Trust & Banking Co.
The balance of shares bought on credit, on the other hand, turned lower for the first time in four weeks.
The outstanding balance of long margin positions stood at 1.25 trillion yen, down 39.33 billion yen.
The back-to-back upswings in share prices in recent weeks prompted margin buyers to unwind their positions and cash in on profits.
The benchmark 225-issue Nikkei average ended the week at 11,847.32, up 316.21 points, or 2.7 percent, on the week.