* Nikkei gains on boost from Fast Retailing
* Topix falls 0.1 pct; NT ratio at second all-time high
* Investors wary of buying ahead of earnings season, 10-day break
By Tomo Uetake
TOKYO, April 12 (Reuters) - Japan's Nikkei share average inched up to close at a four-month high on Friday, but was little changed for the week, as many investors stayed on the sidelines ahead of the U.S. and domestic earnings season and an upcoming 10-day holiday in Japan.
The benchmark Nikkei closed at 21,870.56, up 159.18 points, or 0.7 percent, its highest level since December 5.
However, the broader market was not as rosy as the Nikkei might suggest, with the Topix index dropping 0.1 percent to 1605.40.
The Nikkei/Topix (NT) ratio edged up to 13.62, its second highest level on record, after 13.71 touched in late December.
The benchmark Nikkei was buoyed by a couple of heavyweight stocks.
Fast Retailing Co Ltd soared 7.9 percent to contribute a hefty 162 points, or 0.7 percentage point, to the Nikkei.
The operator of Uniqlo slightly cut its full-year profit forecast after unusually warm weather forced it to slash prices for winter clothes, but the number will still be a record high as its business in China continues to be strong.
SoftBank Group Corp jumped 4.9 percent to boost the Nikkei by 59 points, or 0.3 percentage point, after Uber Technologies Inc filed for an initial public offering, paving the way for the U.S ride-sharing company to go public next month. SoftBank is Uber's biggest investor.
"There are multiple reasons for investors not to buy stocks now. Earnings season is coming up in the United States and Japan, and we are heading into the 10-day holiday period here," said Yasuo Sakuma, chief investment officer at Libra Investments in Tokyo.
To mark the ascension of Japan's new emperor, the government has declared an unprecedented 10-day holiday from April 27 to May 6, which will the longest break ever for Japanese stocks and bonds.
Yaskawa Electric Corp, which usually kicks off the Japanese earnings season, finished the day up 0.1 percent, recouping their initial losses of 4.1 percent, after the industrial robot maker forecast operating profit for the current business year through February to fall 6.6 percent.
Lawson Inc was the worst performer on the main board, diving 12.2 percent, after the convenience store operator cut its dividend forecast for the current financial year by 41 percent.
Other notable movers include Toshiba Corp, which fell 2.7 percent after an agreement to offload its U.S. liquefied natural gas (LNG) business collapsed, a blow for the Japanese conglomerate which has been shedding assets to turn around its business. (Reporting by Tomo Uetake; Editing by Kim Coghill and Sherry Jacob-Phillips)