* Retail investors buying underpins market * BOJ seen keeping policy unchanged but some speculate on surprise * Takashimaya gains after earnings By Hideyuki Sano TOKYO, April 8 (Reuters) – Tokyo’s benchmark index edged up to near 15-year highs on Wednesday after Japanese retail investors ploughed a sizable amount of cash into new stock mutual funds.

Further underpinning the mood was talk the Bank of Japan could step up its asset purchase programme as part of its efforts to drive up inflation towards its 2 percent target, although expectations are for the BOJ to stand pat on policy when it delivers its decision later on Wednesday.

“Japanese shares still look relatively attractive. Some exporters still keep conservative assumption on the exchange rate, and there aren’t any investors who have excessive long position in the market,” said Tetsuro Ii, the president of Commons Asset Management.

The Nikkei rose 0.4 percent to 19,723.42, near its March 23 intraday high of 19,778.60, which was its highest level since 2000.

It has gained 2.7 percent so far this month, helped by the launch of two new equity investment trusts this week, which drew about 160 billion yen ($ 1.3 billion) from investors in total.

Signs of strong appetite from Japanese individual investors were seen as positive in a market which had been largely driven in recent months by public institutional investors, such as government pension funds.

The BOJ has promised to buy 3 trillion yen of equity funds a year and is expected to maintain this pace on Wednesday.

But some investors are speculating the central bank might step up its asset purchase as Japan’s core consumer inflation is slowing, and could briefly turn negative later this year.

Some financial brokerage shares are being bought ahead of the BOJ’s policy announcement, expected some time after 0300 GMT. Brokerage shares gained 0.8 percent, with Nomura Holdings rising 1.2 percent.

Domestic demand oriented shares, such as retailers, remained firm before some of them beging reporting their earnings.

Department store operator Takashimaya rose 1.3 percent after its earning met analyst expectations. Takashimaya has risen over 26 percent so far this year.

Rival Isetan Mitsukoshi rose 1.4 percent, extending its year-to-date gains to 42.5 percent, the fifth best performance among the Nikkei constituents.

The broader Topix rose 0.4 percent to 1,584.05 while the JPX-Nikkei Index 400 gained 0.4 percent to 14,407.33.

($ 1 = 120.1700 yen) (Editing by Shri Navaratnam)