O’Melveny Worldwide

Hiroko Nihei is a litigator specializing in international litigations and arbitrations. She focuses on cross-border dispute resolution matters, including Japanese and US litigations and anti-trust investigations, with a particular emphasis on international commercial arbitrations and contentious intellectual property cases.

She has represented leading Japanese, US, and Asian companies in various and complex arbitration cases concerning international contract disputes under the auspices of the ICC and JCAA.

Hiroko also has experience in litigation ancillary to international arbitrations, including parallel court proceedings and motions to set aside arbitral awards before the Tokyo District Court. Her expertise in intellectual property disputes ranges from defending multinational companies against Internet-related copyright infringement and defamation claims in Japanese courts to acting for Japanese and Asian clients in US patent infringement litigations. She is also a JP domain name dispute panelist for the Japan Intellectual Property Arbitration Center.

  • Acted for an American manufacturer in a major ICC arbitration against a Japanese company arising out of a licensing agreement relating to trade secrets
  • Defended two Asian companies in JCAA arbitration from claims of approximately JPY10 billion brought by a Japanese multinational company
  • Won damages award for a large US multinational in JCAA arbitration against a Japanese company arising out of breaches of a distribution and licensing agreement
  • Successfully represented global manufacturing companies in parallel court proceedings in a Japanese court in relation to a dispute arising from a licensing agreement subject to arbitration
  • Represented several major consumer finance companies in nationwide mass consumer litigation in Japan. Won two Japanese Supreme Court decisions in 2011 and two Japanese Supreme Court decisions in 2017
    • Supreme Court Judgment of March 22, 2011, 236 shumin 225
    • Supreme Court Judgment of July 8, 2011, 237 shumin 159
    • Supreme Court Judgment of July 24, 2017, 71 minshu 6-969
    • Supreme Court Judgment of December 19, 2017, H28 ju 1797
  • Defended a global network service provider in a Japanese litigation from Internet-related copyright infringement claims brought by major Japanese content providers
  • Acted for a multinational Internet security company in several Internet-related copyright infringement and defamation lawsuits in Japan brought by Japanese individual right holders
  • Successfully settled a labor tribunal case before the Tokyo District Court between a leading financial institution and its former employee
  • Represented a global pharmaceutical company in labor disputes before the Tokyo Metropolitan Government Labour Relations Commission and the Tokyo District Court concerning dismissal of employees
  • Acted for a global consulting firm in a business dispute with a Japanese company arising from an outsourcing agreement
  • Successfully settled a dispute arising out of a mega solar project in Japan in favor of an American solar mounting system manufacturer through a construction mediation before a Japanese court
  • Advised a Japanese group company of a multinational financial institution on its application for reexamination before the National Tax Tribunal in Japan concerning its secondary tax liability
  • Achieved a complete victory for a global real-estate investment management and advisory firm in two Japanese litigations concerning its collection of the asset management fees of more than JPY 500 million arising out of a real-estate investment deal involving a complex taxation scheme
  • Served as Japanese law assistant for the sole arbitrator in an ICC arbitration seated in Tokyo in relation to an international trade dispute between a Japanese and Korean company governed by Japanese law
  • Represented two Asian companies in a motion to set aside a JCAA arbitral award before a Japanese court
  • Acted for a Japanese auto components supplier in a US litigation brought by a US government agency alleging claims of US$175 million
  • Represented a Korean electronic equipment manufacturer in a US patent infringement litigation brought by a Japanese patent troll
  • Counsel for an executive of a leading Japanese manufacturing company in connection with US Department of Justice antitrust investigations

Prior to joining O’Melveny, Hiroko worked for Mizuho Bank, Ltd. In addition to her current practice, Hiroko is actively involved in O’Melveny’s pro bono program. She has represented a variety of matters including the following:

  • Advised a Hiroshima-based not-for-profit organization on copyright law issues involved in a multilingual bibliographic database concerning atomic bomb literature
  • Assisted Iraqi and Columbian asylum applicants with refugee applications in Japan in cooperation with the Japan Association for Refugees
  • Represented a not-for-profit organization in the establishment and organization of microfinance funds targeting development projects in Cambodia and Vietnam


  • German
  • Japanese


Bar Admissions

  • Japan


  • Waseda University, Graduate School of Law, LL.M. in Intellectual Property Law
  • University of Oxford, MJur
  • The Legal Training and Research Institute, Supreme Court of Japan, Diploma 
  • Waseda University, B.A., Psychology

Honors & Awards

  • Recognized as “Rising Star: Bengoshi” for Dispute Resolution, The Legal 500 Asia-Pacific (2021-2024)
  • Recognized for Dispute Resolution: Domestic, Chambers Asia-Pacific (2023-2024)
  • Recognized for Dispute Resolution: Domestic, Chambers Global (2023-2024)

Professional Activities


  • Dai-Ichi Tokyo Bar Association
  • Chartered Institute of Arbitrators (MCIArb, CIArb Accredited Mediator)
  • Japan Association of Arbitrators (JAA)
  • Association Internationale pour la Protection de la Propriété Intellectuelle (AIPPI)
  • Japan Association of Industrial Property Law
  • The Copyright Law Association of Japan
  • The Law and Computers Association of Japan

List of Arbitrators

  • Japan Commercial Arbitration Association (JCAA)
  • Japan Intellectual Property Arbitration Center (JIPAC) JP Domain Name Dispute Resolution
  • World Intellectual Property Organization (WIPO) Arbitration and Mediation Center


  • Japan Chapter, Independent Film & Television Alliance 2021 Arbitration Award Enforcement Guide, 4th Edition (October 2021)
  • “Case Studies on International Mediation of Intellectual Property Disputes: Key Takeaways from Actual Cases,” JCA Journal, May 2020 Edition
  • “Arbitrability of Patent Validity Disputes in Japan-Japan as an International IP Arbitration Hub-,” A.I.P.P.I., January 2020 Edition
  • “Arbitrability of Patent Validity Disputes: For Enhanced Use of International Arbitrations in Japan,” JCA Journal, May and June 2019 Editions
  • “How to Select An Arbitrator in International Commercial Arbitration: Major Considerations and Due Diligence,” Business Law Journal, January 2016 Edition


  • “New Japanese Arbitration Case Law: The Osaka District Court’s Pro-Arbitration Ruling,” HK45/HKIAC Newsletter, 6th Edition (October 2015)
  • “A Comparative Study: Is The Singapore International Commercial Court a Rival of Singapore Arbitration?” Business Law Journal, June 2015 Edition
  • “A Nightmare? When You are Caught in Parallel Proceedings: Utilization of Anti-Suit Injunctions and Anti-Arbitration Injunctions in Common-Law Jurisdictions,”Business Law Journal, March 2015 Edition
  • “Key Factors for Japanese Companies to Consider in Selecting an Arbitration Institution,” Business Law Journal, November and December 2012 Editions

Speaking Opportunities

  • “Differences in Arbitral Practice in Japan and Abroad”, Hosted by CIArb YMG Japan Chapter, May 2023
  • “Law and Culture in North Asian Arbitration”, Hosted by ICC YAF, May 2022
  • “International Arbitration Training (Intermediate Level): Practice and Key Points from the Perspective of Arbitral Institutions”, E-Learning Material of Japan International Dispute Resolution Center, April 2021
  • “Strategies for International IP Dispute Resolution During and After COVID-19”, Co-Hosted by Japan Commercial Arbitration Association and WIPO Arbitration and Mediation Center, February 2021
  • “Japan/Asia Update: Recent Developments in International Arbitration and Dispute Resolution”, Hosted by ICDR Young & International, January 2021
  • “Key Points of International Arbitration and International Mediation: What You Need to Know Before Drafting Dispute Resolution Clauses”, Hosted by Nagoya Chamber of Commerce & Industry, December 2020
  • “Basics of International Arbitration and International Mediation: Flexible Dispute Resolution Mechanisms in With / After COVID-19 Era”, Hosted by Engineering Advancement Association of Japan, October 2020
  • International Mediation Webinar, “Post COVID-19: The New Normal for International Dispute Resolution”, Co-Hosted by Japan Commercial Arbitration Association and Japan International Mediation Center, October 2020
  • “Resolving International Intellectual Property and Technology Disputes Outside of Courts: WIPO Mediation and Arbitration”, WIPO Arbitration and Mediation Center, July 2020
  • “Arbitration and Mediation: To improve commercial disputes processing by Vietnam and Japan”, Co-Hosted by Vietnam International Arbitration Center and Research Center for Sustainable Peace of The University of Tokyo, June 2020
  • “APRAG Conference 2020”, Co-Hosted by Thailand Arbitration Center and Asia Pacific Regional Arbitration Group, January 2020
  • “5th IPBA Arbitration Day”, Co-Hosted by Inter-Pacific Bar Association and Japan International Dispute Resolution Center, November 2019
  • “Big Data and Competition”, O’Melveny Competition Seminar, February 2018
  • “How to Select An Arbitrator in International Arbitration - Insights from The Perspective of Counsel, Arbitral Institution, and Arbitrator”, O’Melveny Arbitration Seminar, August 2017
  • “HKIAC Arbitration Clause Negotiation Workshop”, Hong Kong International Arbitration Centre, July 2017
  • “How to Select An Arbitral Institution and Tips for Drafting An Arbitration Clause”, In-House Seminar for A Major Japanese Chemical Manufacturer, August 2016
  • “Typical Stages in International Arbitration”, O’Melveny Arbitration Seminar, February 2016
  • “How to Draft An Arbitration Clause”, In-House Seminar for A Major Japanese Electronics Company, November 2015
  • “Tips for Drafting Arbitration Clauses”, O’Melveny Arbitration Seminar, July 2015
  • “The Essentials of International Arbitration involving Japanese Companies”, Co-Hosted by The Japanese Institute of International Business Law, Inc. and O’Melveny, January 2015
  • “International Arbitration in Asia”, Co-Hosted by LexisNexis and O’Melveny, December 2012