Nintendo's shares fell 10 percent in early trade on Wednesday after they more than doubled in value over the past seven sessions powered by the record-breaking success of the Pokemon Go mobile game.
Pokemon Go, which marries a classic 20-year-old franchise with augmented reality, is now available in 35 countries, mostly in Europe, and technology news site TechCrunch reported the game will be launched in Japan, one of the world's biggest gaming markets, on Wednesday.
Pokemon Company, which created the game along with Nintendo and Google-spinoff Niantic, could not immediately be reached for comment. Nintendo has referred any queries regarding Pokemon Go to Pokemon Company.
Pokemon Go is on its way to becoming the first mobile game to break the $4 billion-per-year wall, beating Candy Crush Saga and Supercell's Clash of Clans, according to Macquarie Research.
Shares of Japan's McDonald's Holdings piggy-backed the Pokemon Go craze, rising 12.5 percent in early trade after TechCrunch reported the fast-food chain operator would become the game's first sponsor.
TechCrunch said the sponsorship will see McDonald's 3,000-plus fast food restaurants across Japan become "gyms", or battlegrounds, for Pokemon collectors.
McDonald's Japan shares soared as much as 23 percent to their highest level since late 2001 on Tuesday, the first day of trade since its stores started giving away Pokemon-themed toys with its Happy Meals last Friday.
McDonald's Japan could not immediately be reached for comment.
($1 = 106.0200 yen)