A successor Japanese government would probably not declare war on Germany

Would a Yonai government declare war on Germany to demonstrate good faith toward the United States?

Probably not; Japan would more likely step back while the United States fought Germany.

A successor government under Mitsumasa Yonai would be unlikely to declare war on Germany as a gesture toward Washington. The United States could concentrate on Germany while Japan withdrew into its own strategic position and resolved its internal crisis. Japan would benefit from the realignment without joining the Allied war. Avoiding a reciprocal declaration would keep Tokyo outside the European conflict.