Investment Watch

The Rising Sun is rising again. The Tokyo Stock Exchange’s main index, the Nikkei-225, gained 224.68 points on Friday to close at 21,695.84--its highest level in four years. The Tokyo market’s rebound this year has raised hopes that Japan’s long bear market is finally over. Many investors have turned bullish because the Japanese economy is rebounding and the yen is weakening against the dollar--good for Japanese exporters. But that same weak yen creates a risk for American investors in Japanese stocks: Currency losses can limit gains achieved by the stocks. In yen terms, the Nikkei is up 9.2% this year; in dollars it’s up 4.9%.