The Nikkei fell 0.22% to 38,403.23, after rising as much as 0.4% earlier in the session. The index rose 1.5% for the week.
The broader Topix fell 0.75% to 2,771.26 but posted a 0.54% weekly gain.
“With the absence of market-moving catalysts, uncertainties surrounding the Middle East tensions dragged investor sentiment,” said Shoichi Arisawa, general manager of the investment research department at IwaiCosmo Securities.
The White House said on Thursday that U.S. President Donald Trump will make a decision within the next two weeks whether to support Israel in its ongoing conflict with Iran.
“On top of the uncertainties about the conflict in the region, the outlook of the U.S. tariff plans remains unclear,” said Arisawa. Uniqlo-brand owner Fast Retailing fell 1.8%, dragging the Nikkei the most. Phone company KDDI fell 1.72%. Game maker Nintendo slipped 4.11% to become the worst percentage loser on the Nikkei.
Chip-related shares rose, with Advantest jumping 4.2% to become the biggest support to the Nikkei. Lasertec rose 4.97% to become the top percentage gainer on the Nikkei.
Machinery maker Amada rose 4.43%
Of more than 1,600 stocks trading on the Tokyo Stock Exchange’s prime market, 27% rose and 69% fell, while 3% traded flat.