In just over a week, the smartphone game "Pokemon Go" has become a giant hit, turning millions of people around the world into monster hunters.

Given the game's promising start, investors are taking another look at Nintendo Co., whose value has shot up by about ¥1.5 trillion since "Pokemon Go" was released on July 6 in the United States, Australia and New Zealand.

Nintendo had been struggling in recent years as people shifted to playing games on smartphones rather than home or hand-held consoles, and the Kyoto-based game innovator was reluctant to enter the field. But last year, Nintendo finally announced it would jump into the smartphone fray.