Why Did Japan Refuse Poland's Declaration of War in WW2?

A fascinating bit of history!

And, from Wikipedia:

During World War II, despite being allied with Nazi Germany, the Empire of Japan along with Italy did not diplomatically support the Nazi invasion of Poland, and the Japanese actively supported the Polish government-in-exile. This decision was dictated by the Japanese distrust of their Nazi allies, who had made a secret pact with the Soviet Union. Thus, the Japanese government decided to continue to rely on Polish spies even after a formal declaration of war by Poland in 1941. The declaration of war from Poland was rejected by Japanese prime minister Tojo Hideki under the pretense that the Polish government in exile was forced to issue it in compliance with its alliance to both the United Kingdom and the United States, making the declaration legally void. This ensured co-operation between the two intelligence services in gathering information on both the Soviet Union and Third Reich. The Japanese agents in Europe during World War II continued to support the Polish struggle for freedom against Soviet Union and Third Reich forces as far as the Japanese interests went. At the turn of 1939 and 1940, the Japanese helped secretly evacuate a portion of the Polish gold reserve, the part held in Lithuanian-annexed Wilno to neutral Sweden. Chiune Sugihara, the Japanese vice-consul in Kaunas, played a key role in the operation and also closely co-operated with Polish intelligence. The Japanese agents also sheltered Polish-Jewish refugees fleeing occupation from both German and Soviet forces, though at first it was done without proper authorization from the Imperial government in Tokyo. Therefore, Chiune Sugihara had to prove to the authorities that the refugees would be traveling through Japan only as a transit country to the United States and not be staying permanently, which eventually led to him gaining full legal approval and assistance from the Government of Japan. Tadeusz Romer, ambassador of Poland in Japan, helped the Polish-Jewish refugees after they arrived to Japan.[8] Throughout the secret alliance, Polish agents never disclosed information about their Western allies and shared information only pertaining to the Third Reich and the Soviet Union.