On the same $90,000 gross, a worker takes home roughly ¥7,518 more per year in Japan than in New Zealand. That gap reflects the tax structure alone — before rent, healthcare, or savings behaviour come into play.
Housing is the first multiplier. Japan has moderate rent pressure, while New Zealand has very high rent pressure. That keeps Japan's nominal advantage closer to a real-world advantage.
Healthcare and pensions go in the opposite direction. Japan runs a universal healthcare model — Universal Shakai Hoken with 30% patient co-pay; very low absolute costs. New Zealand uses a universal model — Universal public healthcare; supplementary cover is common. The country with lower take-home often shifts costs that the other country leaves to your private budget.
Net-of-everything, a relocation decision should weigh comprehensive welfare state in Japan against strong public welfare in New Zealand, plus differences in pension capture, social safety nets, and city-level cost of living.