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Stephen J. DeCosse (Steve)


(T) +81.3.6800.1819
(F) +81.3.5401.2725


  • University of Wisconsin-Madison (J.D.; Senior Articles Editor, International Law Journal); Princeton University (B.A.)

Bar Admissions

  • Registered Foreign Lawyer in Japan (Daini Tokyo Bar Association) and California

Steve DeCosse focuses on public and private cross-border M&A and investments for strategics, trading houses, and private equity firms. He has handled major inbound and outbound semiconductor M&A deals in recent years, some of which relate to IoT, including various sensor technologies applicable to, for example, smartphones, autos, drones, and utilities. His recent outbound experience includes energy, energy storage including Li-ion, transport and logistics, grain, water, food, and health care. His significant inbound experience extends to hospitality and resorts, auto parts, solar, digital ad measurement, parking services, and medical devices.

Steve manages anticorruption due diligence for Japanese companies engaged in outbound M&A or projects. He is a member of the Association of International Petroleum Negotiators.

He is currently involved in an Asia-wide pro bono project focusing on human trafficking in six southeast Asian countries.

Honors & Distinctions

  • Cited as a leading lawyer in 2019 in Chambers Global, Chambers Asia-Pacific, and The Legal 500 Asia Pacific in corporate/M&A, where clients say ‘his advice is practical and prompt’ and he ‘understands exactly what clients need’


English, Japanese
Stephen DeCosse De Cosse Steven Steve