* Nikkei down 0.9 percent, Topix falls 0.5 pct
* Losses in Chinese market drag down China-related shares
By Ayai Tomisawa and Antoni Slodkowski
TOKYO, Dec 20 (Reuters) - Japan's Nikkei dropped 0.9 percent in thin trade on Monday, with sentiment soured by a declining China market.
The Nikkei fell 87.42 points to 10,216.41, approaching support at 10,116.53, its 25-day moving average, a gauge closely followed by Tokyo investors.
The broader Topix index declined 0.5 percent to 898.55.
Asian shares eased, led by a drop of as much as 3 percent in China's key stock index as a shortfall of money flows ahead of the year-end in a tight monetary environment pressured the market. (Editing by Edmund Klamann)