Nintendo Co. is easing into its newfound role as a mobile game publisher, but not fast enough for investors expecting a Mario-scale hit.

The video-gaming company revealed plans to introduce two new smartphone titles in the coming year, even as it forecast net income and revenue short of analysts' estimates on plunging sales of the Wii U console and 3DS handhelds. Shares fell as much as 9 percent in Tokyo trading.

Nintendo, known for popularizing consoles more than three decades ago, is starting to embrace the age of mobile gaming. So far, the signs are encouraging: Miitomo, a new free-to-play messaging app, has attracted more than 10 million users since its debut last month.