The game, which marries a classic 20-year-old franchise with augmented reality, has taken the world by storm despite having been launched in only five countries: the United States, Australia, New Zealand, Britain, and Germany.

“Why limit it?” John Hanke, chief executive of Niantic, which developed Pokémon Go jointly with Nintendo affiliate Pokemon Co., said in an interview with Reuters on Friday.

He declined to go into a detailed time frame for further rollouts but noted that the company’s first location-based augmented reality game, Ingress, had taken a month or two to reach that number of markets.

His comments helped Nintendo (NTDOY) shares on Friday surge another 10%, setting a record in daily trading volume for an individual stock on the Tokyo bourse. The shares have climbed 86% in just over a week, adding $17 billion in market value.

He confirmed that the game would soon be coming to Japan and that he expects “ultimately to launch” the game in South Korea, where Google’s mapping functions are restricted due to security issues with North Korea.

Hanke said Niantic, which was spun off from Google (GOOG) last year, is working on the mapping issue. “There are solutions to that,” he said.

South Korea is the world’s fourth-biggest gaming market after China, the United States, and Japan, according to Amsterdam-based research firm Newzoo.

But he was more reticent about prospects for a launch in China, saying only that there are regulations that have to be considered.

Hanke said the company is considering introducing a sponsorship scheme similar to one it has with Ingress, which designates sponsors’ stores and vending machines as spots in the game.

Sponsors pay per customer visit, providing a revenue stream in addition to in-app purchases. Niantic currently has eight corporate sponsors for Ingress globally, including SoftBank Group (SFTBY), and the number is likely to be similar for Pokémon Go, he said.