"Since last year, Sony has been engaged in discussions with Fujitsu concerning possible co-operation in the field of Internet-related business. However, we wish to announce today that we have mutually agreed to discontinue these discussions," a statement from Sony read.
The discussions centred around Nifty, Fujitsu's Internet arm, and So-net, which is run by Sony. Nifty had 5.2 million subscribers in March, making it Japan's number one ISP, while So-net had only 2.2 million users.
The two companies had discussed an alliance or possible acquisition of Nifty by Sony, which was keen to build up its consumer ISP business. Sony has already used an acquisition of ISP JustNet to expand its reach by 340,000 users and could still be looking at additional targets.
According to a report in the local media last week, Sony is in talks with Vodafone regarding an acquisition of Japan Telecom's ISP business.
Vodafone purchased Japan Telecom, owner of cellular carrier J-Phone, last year, and is understood to be keen to offload the non-mobile parts of the business.
Sony declined comment on that most recent report.
"We are not commenting on the existence of negotiations or otherwise in regard to other Internet tie-ups," said Gerald Cavanagh, a spokesman for Sony in Tokyo.