The division will be relaunched, with a focus on developing media and advertising for broadband. The new name of the unit has not been revealed, but Ikuya Tanaka, currently director of Dentsu's sports marketing division, has been named president of the operation.
The move will see Intervision, Sony's advertising subsidiary, retain Sony as a client, but will also seek new business from other clients.
It plans to offer a wide range of services, from the traditional media planning and buying, to interactive marketing, developing new technologies for market and providing content.
It is part of Sony's strategy to integrate its products, including TVs, stereos, videos and its ISP So-net. Sony chairman and chief executive Nobuyuki Idei said: "We must become more efficient in the way that we advertise."
Dentsu is Japan's largest ad agency, reportedly accounting for some 25% of ad revenue in the country.
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