Herbert Smith Freehills (HSF) is now down to six partners in Tokyo with the departure of its head of corporate for Japan, James Robinson.

The firm is left with just two corporate partners in the Japanese capital – Graeme Preston and Andrew Blacoe – with another four on the disputes side, including its office managing partner and head of disputes for the region, Peter Godwin.

Robinson, whose focus is M&A and antitrust and who worked for the firm in Tokyo for 10 years after training with Herbert Smith in London, is understood to be moving to US outfit Morrison & Foerster (Mofo).

Licensed to provide English law counsel in Japan, he typically acts for Japanese clients doing business abroad, as well as advising international clients – usually in the manufacturing, media, private equity or finance sectors – on setting up in the country.

His move will provide a further boost to the Japan offices of Mofo – which is currently the biggest international firm in Japan with more than 120 lawyers – 50 of whom are Japanese.

HSF has seen several partners depart or relocate from its Tokyo office in the last four years.

Former office head and corporate partner Steve Lewis moved to Bingham McCutchen in 2010, while James Watson, who was previously co-head of the energy and infrastructure practice in Japan, joined Vinson & Elkins in April 2012.

Another partner David Clinch, now head of the Asia energy practice, relocated to Hong Kong in the middle of 2012, followed by the transfer of Rebecca Major to HSF's Paris office in August last year and the retirement of its remaining head of energy in Tokyo, David Laurence at the end of last year.

In a statement HSF said it remained focused on cross border transactions and disputes, and had a long history in Tokyo after opening in 2000.

Godwin added that plans had been in place for some time "to increase partner numbers in Tokyo".