So about the PS5 being only slightly behind the PS4 in sales launch aligned, I think that doesn't really tell the whole story, considering the numerous reports about Chinese resellers buying PS5s from Japanese retailers throughout 2022 to 2024. There was a big price hike
last September which looks like has mostly put a stop to that.
Anyway, the reason I'm bringing this up is because of the recent news that Wukong sold an estimated 3.5M copies in China on PS5, which suggests that the install base there is significant, with many consoles being from the 'gray market', as in imported from HK, TW, and JP. So this is something to take into account when discussing the install base of PS5 vs. PS4 in Japan.
Bic Camera's system records passport numbers to identify bulk purchasing
asia.nikkei.com