The smartphone game "Neko Atsume" (Cat Collecting) is gaining a worldwide following for its nonsense and adorableness.

The Japanese app has already logged more than 5.5 million downloads since it was launched in October. Although not available in English, 30 to 40 percent of the downloads have recently taken place overseas, mainly in China and North America, said Yutaka Takazaki of Hit-Point Co., developer of the game.

"When we developed this app in the beginning, we were focusing on a niche market of Japanese cat lovers," Takazaki said. He attributed the game's surprising success to its very simple structure and adorable graphics.