Yahoo Japan, the Yahoo Inc. subsidiary, has furthered its mobile ambitions after it announced the $12.8 million (1 billion yen) acquisition of Tokyo-based mobile content firm Community Factory, as Japanese tech blog Asiajin reports.

The deal is a rare example of a big company acquisition in the country, as Asiajin notes, and, for its investment, Yahoo Japan will get its hands on Instagram-like Decopic, which boasts 7 million iOS and Android users, 6-million user strong Mixi client Kentei and more.

Home-grown Facebook rival Mixi is the largest Community Factory investor, by virtue of the 40 percent that its Mixi Fund — set up to promote and encourage Web startups in Japan — holds.

Yahoo Japan is quite a different entity from its parent Yahoo Inc., which was said to be pursuing a sale of its 35 percent share of the Japan-based company. Despite increased optimism following the appointment of Marissa Mayer, Yahoo Inc. has struggled while Yahoo Japan continues to march on as a key Internet player in the country.

Its Yahoo Japan Web portal is the country’s most visited site, according to Alexa, while mobile accounts for an impressive 20 percent of its monthly page views (PDF).

This year it has increased its focus on mobile — with smartphone adoption growing in Japan — and it has a browser for Android, having added its own app store for the Google-owned mobile platform in 2011.

New CEO Manabu Miyasaka has been behind the charge, and he has publicly stated his intention to strengthen the company’s mobile and social footprints, making Community Factory an ideal acquisition.

Yahoo Japan has actually followed Mixi’s lead, setting up its own fund to invest in Web startups last week. The initiative has a reported war-chest of $12.8 million, but it is not related to today’s news.

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