I think the question presupposes that Nazi Germany and Imperial Japan needed the "living space" they supposedly sought during the Second World War. I don't think that's valid. Ultimately you could argue that Germany only needed extra space if it was to become the great empire that Hitler envisaged. Obviously with their defeat in '45 this never happened and thus they needed no substitutes.

But the notion of lebensraum likely went beyond needing extra space for state-encouraged expansion. Scholars have long discussed Hitler's true motives for the war, and beyond the surface level rhetoric of lebensraum, have come up with issues of racism, cultural superiority, the need to retake lost terrtiory, the desire to regain lose pride, and many others.

Interestingly, Hitler co-opted the notion of Lebensraum from Imperial Germany, where the term denoted a push to acquire overseas colonies. But in place of colonies, he sought territory on the European continent itself.