McDonald's Japan shares have jumped as media reports suggest Nintendo's Pokemon Go will be launched there in a deal with the fast food chain.
The hugely successful smartphone game is available in the US and many other countries, but not in Japan yet.
McDonald's Japan jumped more than 11%, but Nintendo fell almost 10%.
The gaming company's shares have soared in the past week, more than doubling its market value, on the success of Pokemon Go.
Both The Wall Street Journal and industry website TechCrunch having cited unnamed sources saying that the game will be launched in a tie-up with the fast food company, with the latter suggesting the launch will happen as early as Wednesday.
Tokyo's Nikkei 225 was down 0.7% to 16,605.46 points in early trade.
Elsewhere in Asia, South Korea's Kospi was down 0.4% to 2,009.87 points, while Australia's ASX/200 was 0.4% higher at 5,473.80.
Commodity giants were among the big losers of the day, with Rio Tinto losing more than 2% while BHP was down more than 4%.
In China, Hong Kong's Hang Seng was up by 0.4% to 21,760.03 while the Shanghai Composite traded flat.