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Kenji Tosaki

Partner

Tokyo Office

Kenji Tosaki

Partner

Tokyo Office

Tel

+81-3-6889-7206

Fax

+81-3-6889-8206

Contact

People

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

Languages

Japanese, English

Qualifications

2008, Japan (Dai-Ichi Tokyo Bar Association)

Practice Areas

Languages

Japanese, English

Qualifications

2008, Japan (Dai-Ichi Tokyo Bar Association)

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

Kenji Tosaki

Kenji Tosaki

Education/Professional Experience

Seminars

Patent Linkage System in Japan – Two Recent Court Decisions on Unfair Competition and Patent Linkage System

Due process of handling technical disputes in patent infringement lawsuits

Japan a Paradise for Machine Learning, Not Generative AI

New Developments in Intellectual Property Law – 2023 Amendments and Recent Key Issues (NO&T IP Forum 2023)

Publications

Update: A Second Court Decision addressing Patent Linkage and Unfair Competition

Judgment rendered by the Grand Panel of the Intellectual Property High Court on March 19, 2025, regarding the patentability of compositions which contemplate medical procedures both before and after manufacture

Patents: – The Principle of Territoriality: Two Notable Judgments of the Supreme Court of Japan rendered on March 3, 2025

The International Comparative Legal Guide to: Digital Health 2025 – Chapter 17 Japan

Awards

High evaluation received in the 2026 Edition of The Best Lawyers in Japan™ and Best Lawyers: Ones to Watch in Japan™

NO&T highly commended in IP STARS 2024

High evaluation received in the 2025 Edition of “The Best Lawyers in Japan”

Topics

Announcing Two New Partners of NO&T

Kenji Tosaki joins Nagashima Ohno & Tsunematsu