I mean if you restrict things enough than any metric is possible. Looking at 500k people (your link) out of 37m (Tokyo Prefecture) or 9m (Tokyo 23 Wards) I feel isn't the best metric.
Probably best to just restrict both NYC/Tokyo to their urban areas and their respective housing costs which is what this blog post is originally about. Otherwise, you can just say there are "free" homes in "Tokyo" because there's a lot of abandoned homes in the rural parts that you can squat.
For Tokyo, I think discussions about population change should be focused on the 23 central wards. Here's a more up-to-date source: https://www.toukei.metro.tokyo.lg.jp/jsuikei/js-index.htm (it seems to be 14mil today vs 9mil in 2016)
