TOKYO — “Pokemon Go” fans in Japan began tweeting about it as soon as it was available this morning, and the Pokemon Co. and the developer of the augmented reality game, U.S.-based Niantic, confirmed its launch.

“Pokemon Go” is expected to be a huge hit in Japan, the country of the character’s birth. Fans have been eagerly awaiting its release since it first came out more than two weeks ago in Australia, New Zealand and the United States, and then spread to become a blockbuster hit in more than 20 countries.

One of the Japanese creators of the game apologized for the delay in a video with the American head of Niantic posted on the internet. “To everyone in Japan: I am sorry to make you wait for so long,” said Jyunichi Masuda, the head of development at Game Freak, the developer of the original Pokemon game.

In Pokemon Go, players search for digital creatures that pop up on smartphone screens as they move through real-world locations. The game’s success has sent the stock price of Nintendo Co. soaring. The Japanese game maker, in partnership with Game Freak, released the original Pokemon game in the mid-1990s, and owns the trademarks to all the game’s characters.

The launch in Japan includes a tie-up with McDonald’s Japan.

Financial details have not been disclosed, but McDonald’s said that about 400 of its 2,900 restaurants in the country are designated as “gyms” where players can battle on their smartphones. The other 2,500 are “Pokestops,” where players can get “Poke Balls” and other items they need to play the game.

Because the game uses GPS, it can drive potential customers to a store in a way that other games cannot.

In Akihabara, 19-year-old student Yuchi Mori said he was undeterred by the multiple reports of “Pokemon Go”-related traffic accidents and other mishaps. He downloaded the game as soon as a school exam ended Friday morning.

As anticipation built toward the Japan release this week, the government issued nine safety-related rules for “Pokemon Go” players to follow. Niantic CEO John Hanke asked users to play with care.

“When you go out to play, keep your head up, look around, enjoy the world around you and be safe,” he said in the video message.