Supercell Oy started the year trying to break into the Japanese smartphone game market. By October, it had struck a deal with the nation's second-richest man that valued the maker of "Clash of Clans" at $3 billion.

The Finnish game-maker is seeking a bigger slice of Japan's market for downloaded games, which is forecast to triple to $3 billion this year, amid a shift to smartphones, Supercell co-founder Ilkka Paananen said in an interview. Billionaire Masayoshi Son's SoftBank Corp. led a $1.53 billion agreement for a 51 percent stake, a deal that was completed last week.

Supercell's bet on a country with a declining population is paying off as mobile users shift from feature handsets to Apple Inc. devices and phones using Google Inc.'s Android software. After Supercell began working with Gungho Online Entertainment Inc., which is led by the SoftBank president's younger brother, Taizo Son, its flagship title skyrocketed to among the country's top 10 mobile downloaded games, said Paananen.