He is also the author of the “Matsumoto Draft”, a proposal for revision of the Constitution of the Empire of Japan in the immediate post-war period.

He travelled to Europe from 1906 to 1909 for further studies and returned to Tokyo Imperial University in 1910 to join as a full professor.

In 1919, Matsumoto accepted a post on the board of directors of the South Manchurian Railway Company and eventually rose to the position of vice-president.

[1] From 1923, under the second Yamamoto and the Kiyoura administrations, he served as Assistant Director-General of the Cabinet Legislation Bureau.

Matsumoto returned to the government after World War II under the Shidehara administration as a Minister of State, in charge of the “Committee to Study Constitutional Problems” established by order of General Douglas MacArthur to study constitutional amendment, informally known as the “Matsumoto Committee”.