Germany (1985) 

Registration in Japan

Registered Foreign Lawyer (The Laws of the Federal Republic of Germany) (2000)

Bar Association

Dai-ichi Tokyo Bar Association
German Bar Association
Inter-Pacific Bar Association


The University of Cologne Law School, Koln high court, the first judicial examination (1982)
Berlin high court judicial mastering, the second judicial examination (1985)


Gassner, Siederer (now Gassner, Groth, Siederer) (Berlin) (1985)
Sonderhoff & Einsel Law Office (1990-1997)
Haarmann, Hemmelrath & Partner (1997-2000)
Janssen Foreign Law Office (a joint venture with Asahi Koma Law offices), Managing Partner (2000-2007)
Tokyo Aoyama Aoki Koma Horitsu Jimusho Baker & McKenzie Gaikokuho Jimu Bengoshi Jimusho Gaikokuho Kyodo Jigyo (now Baker & McKenzie (Gaikokuho Joint Enterprise)), International Partner (2007-2013)
Janssen Foreign Law Joint Enterprise with Atsumi & Sakai, Managing Partner (July 2013-)


German-Japanese Juridical Association
Lifetime honorary member of the board of the German Embassy's Charity Fund (the Botschafter Dittmann Fonds of the German Embassy)


  • "Industrie 4.0 and the Internet of Things (IoT) in Germany," KOKUSAI SHOJI HOMU Vol. 44, No. 7, Japanese Institute of International Business Law, Inc. (July 2016) [Co-author]