Would the alliance rapidly decolonise Japan?

Could alliance with Britain produce a Japanese decolonisation movement by 1944?

No rapid transformation is likely; Japan was not at the same stage as Britain's evolving empire and Commonwealth.

Britain's dominion process does not transfer neatly to Japan. Yonai could moderate foreign policy without advocating the abandonment of Korea, and Japan's imperial and economic development followed a different path. Allied cooperation may alter behaviour and institutions, but it does not erase Japanese colonial commitments within a few years.