Kei Matsumoto

Kei Matsumoto
– Member of Daiichi Tokyo Bar Association –


Kei Matsumoto has been consistently engaged in crossboarder legal practice in business law field since he was qualified in 2001.

Prior to joining this firm, Matsumoto worked at Baker & McKenzie (Gaikokuho Joint Enterprise) more than 10 years as a partner. Also, he was in the patent litigation division of the Silicon Valley Office of Weil, Gotchal & Manges LL.P from 2006 to 2007, where he handled patent litigation involving Japanese companies and other litigation in the US. He also has considerable experience in dispute resolution cases inside and outside the courts, practice in relation to healthcare and life science industry as well as corporate/M&A related cases. He is a native Japanese speaker and is fluent in English.

Kei Matsumoto


  • Northwestern University School of Law (LL.M.) (2006)
  • The University of Tokyo (LL.B.) (1999)

Practice Focus

  • IP litigation and dispute cases, in particular local and international patent dispute
  • Licensing and other transaction in relation to IP
  • Litigation and dispute resolution
  • Transaction such as joint development and license and other practice in healthcare and life science industry
  • General advisory to companies in IT industry
  • Practice in relation to real estate and hotel development
  • Data protection law advisory

Representative Clients, Cases or Matters

  • Represented many local and foreign clients in patent infringement litigation, preliminary injunction cases based on patent infringement and actions against patent invalidation trial decision in Japanese courts
  • Represented clients in many cases related to the Unfair Competition Prevention Act
  • Worked on patent litigation concerning optical discs and semiconductors in the US where Japanese companies were involved.
  • Worked on many joint development and license matters in pharmaceutical industries
  • Worked on many development cases using AI
  • Researched the legal systems for protection of trade secrets in 7 countries including Japan and reported the results for “The commissioned project of industry and economy in 2014 (research and study regarding protection of trade secrets)” of the Ministry of Economy, Trade and Industry.
  • Represented a client in negotiations with respect to an acquisition of a major hotel by conducting due diligence and drafting contracts.
  • Represented and advised a major US IT company (from Japan’s end) with respect to review of contract and its expansion in the Japanese market.

Publications and Articles

  • Co-author, “Protecting IP Licenses and Jointly Owned IP in the Age of COVID-19: Insolvency and Force Majeure Events under Japanese Law,” GRUR International, Volume 70, Issue 5, May 2021, Pages 463-485, German Association for the Protection of Intellectual Property and Copyright e.V, June 2021
  • Author, “Intellectual Property Law and Business Seeds: No. 29 Unitary Patent and Unified Patent Court in Europe” Jurist 1542, Yuhikaku, May 2020, Language: Japanese
  • Author, “Proactive US class action strategy — preventative data likage measures,” Business Law Journal, LexisNexis, April 2018, Language: Japanese
  • Co-author, “Proactive US class action strategy — preventative measures and basic insights into preventing class actions,” Business Law Journal, LexisNexis, August 2017, Language: Japanese
  • Co-author, “Trade secret protection programs and practices in foreign countries: Discussing viable legal actions in the U.S., Korea, China, Taiwan and Germany,” Business Law Journal, Lexis Nexis, May 2016, Language: Japanese
  • Author, “Technical information leakage prevention and countermeasures,” Business Homu, Chuokeizai-Sha, September 2012, Language: Japanese
  • Co-author, “Cloud Computing and the Law,” Kinzai, October 2011, Language: Japanese
  • Co-author, Business Law, Chuokeizai-sha, 2004, Language: Japanese
  • 「Amendment to the Labor Standard Law of Japan」『 Asian Legal Business』(2004年)
  • Chapter, “Amendment to the Labor Standard Law of Japan,” Asian Legal Business, 2004, Language: English


  • Presenter, “Precaution and countermeasure for information leak and divulgation in your companies – in consideration of role of auditors -”(Training Workshop at Japan Audit & Supervisory Board Members Associations Chubu Branch, October 2021)
  • Presenter,“CIO/CISO from Lawyer’s eyes” (<> online seminar. AOS Data, Inc. January 2021)
  • – Panelist,“Comparison of handling trade secret and shared data with limited access in AI service agreement”(APPTraS. December 2020)
  • Presenter, “CIO/CISO from Lawyer’s eyes” (NCA Legal System Working Group of NipponCSIRT Association. November 2020)
  • Presenter,“How to deal with the amendment to the Unfair Competition Prevention Act and Patent Act etc.”(APPTraS. July 2018)
  • Presenter,“Points of the amendment to the Unfair Competition Prevention Act this time and its impact, how to deal with in practice, impact on oversea transaction and relationship with TPP”(APPTraS. February 2016)
  • Presenter, “Private use and indirect infringement – including issues concerning cloud computing -” JBMIA, Japan Business Machine and Information System Industries Association, 1 March, 2013
  • Presenter, “Cloud computing and the law – a focus on IP and surrounding issues,” LES Japan, 27 September 2012
  • Presenter, “Legal Issues and Practical Solutions in Popularizing Cloud Computing,” Japan Planning Institute, 5 April 2012
  • Panelist, “Evidence Gathering and E-discovery Issues in International Matters, Key Developments in the U.S. and Japan,”Intellectual Property Issues Facing Japanese Companies and Cross Border Business Seminar, Daiichi Tokyo Bar Association and the International Law Section for the State Bar of California, 4 November 2011)


  • New York, United States (2007)
  • Japan (2001)


  • Japan Federation of Bar Associations – Member
  • Dai-ichi Tokyo Bar Association – Member
  • New York State Bar Association – Member

Pro Bono and CSR

Kei actively works for juvenile protection cases.


English, Japanese

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