I have genuinely never in my life seen any trader anywhere mention JPY volume or pay any attention to it. That says enough about adoption and interest there.
in 2017, japan was a big deal. i always had a tab open for bitflyer BTC/JPY, and so did other traders i know of. at one point BTC/JPY even represented 60% of all reported trading volume:
https://www.cnbc.com/2018/06/22/bitcoin-tumbles-after-japan-watchdog-orders-exchanges-to-review-business-practices.htmlafter strict crypto regulations were passed, japanese exchange volume plummeted and japan fell off the radar. most of it was fake to begin with i'm sure, but fake volume can have a powerful effect. before 2017, we used to follow chinese exchanges for the same reason.