Awards
Kenji Tosaki is a partner at Nagashima Ohno & Tsunematsu. His practice focuses on dispute resolution. He specializes in intellectual property litigation and complex commercial litigation, and he also covers the area of TMT including data protection matters.
In the area of intellectual property litigation, he has been handling both IP infringement litigations and IP invalidation litigations before the IP High Court, the Supreme Court, District Courts and Japan Patent Office. His IP expertise includes a wide variety of IP matters (patents, copyrights, trademarks, design rights, unfair competition and trade secrets) in many areas, such as pharmaceuticals, telecommunications, electronics, social games, medical devices and chemicals. He also provides pre-litigation counseling, including infringement/invalidity analysis.
In the area of complex commercial litigation, he gives advice on matters such as securities law and cross-border contract.
He is a member of the Japan Association of Industrial Property Law, the Copyright Law Association of Japan and AIPPI Japan (International Association for the Protection of Intellectual Property). He is also an active member of TechLaw Group (http://techlaw.org/), which is a global network of technology savvy law firms.
Practice Areas
Education/Professional Experience
- 1996
- The University of Tokyo (LL.B )
- 1998 - 2000
- Judge of Tokyo District Court
- 2000 - 2002
- Judge of Hachioji Branch of Tokyo District Court
- 2001 - 2002
- Visiting Scholar, Southern Methodist University Dedman School of Law
- 2002 - 2004
- Deputy Director, Planning and Legal Division, Planning and Coordination Bureau, Financial Services Agency
- 2004 - 2004
- Judge of Tokyo District Court
- 2004 - 2005
- Deputy Director, Office for Privitization of Japan Post, Cabinet Secretariat
- 2005 - 2006
- Judge of Tokyo District Court (Intellectual Property Division)
- 2006 - 2008
- Judge of Takamatsu District Court
- 2008 -
- Nagashima Ohno & Tsunematsu
- 2010 - present
- Member of Policy Commission, Type II Financial Instruments Firms Association
- Apr 2011 -
Sep 2011 - Adjunct Lecturer, Sophia Law School
- 2013 - present
- Partner, Nagashima Ohno & Tsunematsu
- 2016 - 2017
- Chairman, Panel of Experts of Research regarding IP Strategy of Field in Regenerative Medicine, Japan Agency for Medical Research and Development
- 2017 - 2018
- Committee Member, Research regarding IP Strategy and Optimization of Practical Use in Biopharmaceutical, Japan Agency for Medical Research and Development
- 2017 - 2018
- Chairman, Panel of Experts of Research regarding the handling of experimental research data in deriving achievements in the medical field, Japan Agency for Medical Research and Development
- 2018 - 2019
- Committee Member, Research regarding IP contracts, etc., for deriving investigator - initiated clinical trial data, Japan Agency for Medical Research and Development
- 2020 -
- Committee Member, Standing Committee on Enforcement, AIPPI (International Association for the Protection of Intellectual Property)
- 2021 - present
- Committee Member, Center for Appointment of Judges from among Lawyers, Japan Federation of Bar Associations
Awards
Seminars
-
September 15, 2025 (Mon) 09:30 - 11:00Pssst! Recent Trends and New Concepts in Trade Secret Protection and Enforcement (Panel Session)
- Kenji Tosaki (Moderator)
PACIFICO Yokohama North
- Intellectual Property
- Dispute Resolution
-
July 9, 2025 (Wed) - October 23, 2025 (Thu) 16:00Key Points of the latest revision of the Trade Secrets Management Guidelines and Practical Issues ~Part 2 Management of Emergency Situations~
- Kenji Tosaki
- Takahiro Hatori
Online (On-Demand)
- Intellectual Property
- IP Transactions
-
May 23, 2025 (Fri) - October 23, 2025 (Thu) 16:00Key Points of the latest revision of the Trade Secrets Management Guidelines and Practical Issues ~Part 1 Preparation in Normal Times~
- Kenji Tosaki
- Takahiro Hatori
Online (On-Demand)
- Intellectual Property
- IP Transactions
-
April 7, 2025 (Mon)Patent Linkage System in Japan – Two Recent Court Decisions on Unfair Competition and Patent Linkage System
- Kenji Tosaki
Vision Center Tokyo Toranomon
- Dispute Resolution
- IP Disputes
- Intellectual Property
Publications
-
Articles
The International Comparative Legal Guide to: Patents 2026 – Chapter 14 Japan
(October 2025)
Kenji Tosaki
- Intellectual Property
- IP Transactions
- IP Disputes
-
Newsletters
First IP High Court Decision on Patent Linkage and Unfair Competition
Kenji Tosaki, Takahiro Hatori, Nozomi Kato (Co-author)
- Intellectual Property
- Dispute Resolution
-
Articles
The Legal 500: 9th Edition Intellectual Property Country Comparative Guide – Japan
(September 2025)
Kenji Tosaki
- Intellectual Property
- IP Transactions
- IP Disputes
-
Newsletters
Intellectual Property High Court orders generic drug companies to pay approximately JPY 21.7 billion in total in a patent infringement lawsuit (Judgment rendered May 27, 2025)
Kenji Tosaki, Ryo Tonomura (Co-author)
- Dispute Resolution
- IP Disputes
- Intellectual Property