The High Contracting Parties solemnly declare in the names of their respective peoples that they condemn recourse to war for the solution of international controversies, and renounce it, as an instrument of national policy in their relations with one another.
The High Contracting Parties agree that the settlement or solution of all disputes or conflicts of whatever nature or of whatever origin they may be, which may arise among them, shall never be sought except by pacific means.Kellogg-Briand Pact 1928
The Contracting Powers, other than China, agree:
(1) To respect the sovereignty, the independence, and the territorial and administrative integrity of China;Treaty Between the United of States of America, Belgium, the British Empire, China, France, Italy, Japan, the Netherlands, and Portugal. Signed at Washington February 6, 1922.
Matsumoto in his book "the failures Japan made" argues that the invasion of Manshu was the direct violation of two treaties Japan concluded.
The extreme rightist would argue that Manshu was not a part of China.
Whatever they may say, it would be difficult to say that Japan didn't violate Kellogg-Briand Pact.