The Nikkei fell 1.30 per cent today on its way to its lowest close in two months.
The fall came as investors sold Canon shares and other exporters after a sharp fall on Wall Street and concerns about the strong yen.
The Nikkei was down 216.36 points at 16,385.42 earlier this morning. If it closes at this level, it will book its lowest finish since March 16th and its fifth straight loss.
The broader TOPIX index was down 0.64 per cent at 1,677.39.
The yen was at around 109.50 to the dollar. On Friday it hit an eight-month high of 109.29. A strong yen is a minus for Japan's exporters as it eats into profits when earnings from abroad are brought home.
Canon, which makes more than 75 per cent of its sales abroad, fell 4.2 per cent to 8,310 yen. Likewise, TDK, whose bulk of sales come from overseas markets, sagged 0.6 per cent to 9,420 yen.
Auto makers, dependent on growth in abroad, gave in to the yen's climb. Toyota fell 1.7 per cent to 6,260 yen and Honda Motor declined 2.3 per cent to 7,670 yen.
In the telecom sector, Nippon Telegraph and Telephone jumped 5.1 per cent at 559,000 yen after the world's largest telecoms group by revenue forecast growth in profits and revenues this year thanks to growing data communication services.