If a massive billboard by Shibuya crossing is a barometer of trends in Japan, then the latest ad for the cryptocurrency exchange DMM Bitcoin, featuring a Japanese celebrity coated in gold, may be a sign of how cryptocurrencies have taken center stage in both the advertising media and the broader national conversation in Japan.

"When I was in London I would see ads all over Facebook, but never on TV or in the streets like this," said a 20-year-old British tourist as he stood under the billboard last week.

While consumers have been inundated with such advertisements over the past few months, the exchanges are now facing more pushback on how they promote trading services of ultravolatile virtual currencies. Facebook recently banned cryptocurrency-related ads and one Japanese industry group has suggested self-regulation in light of the Coincheck Inc. hacking incident.