Kei Umebayashi is a partner at Nishimura & Asahi and previously worked at the Special Investigative Section of the Tokyo District Public Prosecutors Office, where he obtained extensive experience and know-how in criminal investigations.
He is expert at gathering evidence and conducting hearings.
He mainly handles cases in which the executives or officers of a company leaked, intentionally or accidentally, the company’s confidential information, including customer data and business secrets.
He deals with matters conducted by Japanese authorities, including the Securities and Exchange Surveillance Commission (SESC) and the Fair Trade Commission.
Additionally, he gives valuable advice concerning a variety of other matters, such as insider trading, antitrust law, leniency applications under antitrust law, and inquiries by the US Department of Justice, European Commission and other foreign authorities when a company is targeted by them due to alleged violations of antitrust laws.

Recent activities


Top Tier in The Legal 500 Asia Pacific 2020



The NIKKEI "Most successful lawyers in 2018"



Getting the Deal Through - Government Investigations 2017 (Japan Chapter)



The University of Tokyo (LL.B.)

Professional experience

2018 -
Member of Task Force organized in the Railway Bureau of MLIT
2017 -
Member of Task Force (final inspection issue) organized in the Road Transport Bureau of MLIT
2016 - 2017
Member of Task Force (fuel consumption issue) organized in the Road Transport Bureau of MLIT
2014 -
Part-time professor of Keio University Law School
2014 -
Member of the Independent Committee of Japan Sport Council
2011 - 2012
Counselor of the Ministry of Internal Affairs and Communications
2005 - 2007
Executive Assistant to Deputy Chief Cabinet Secretary
Public Prosecutor, Secretarial Division, Ministry of Justice
2003 - 2004
Public Prosecutor, Chiba District Public Prosecutors' Office
2002 - 2003
Public Prosecutor, Criminal Affairs Bureau of the Ministry of Justice
1999 - 2002
First Secretary, Japanese Embassy, U.K.
1998 - 1999
Public Prosecutor, Criminal Affairs Bureau of the Ministry of Justice
1991 - 1997
Public Prosecutor, Tokyo, Fukuoka, Yokohama and Shizuoka District Public Prosecutors' Offices