Dead drops? One guy talks, they have a drop site. Law enforcement knows how to do stakeouts. Wait until someone comes to pick up the cash from the drop site, tail him to wherever he goes next.
Deposit it in real banks and transfer it somewhere? Okay, now you don't even need a participant to cooperate, you can just identify him and pull his bank records.
Maybe they convert it to BTC. Are there mixing services doing enough volume to really be untraceable? Otherwise investigators can watch it on the other side and see whose bank account it gets converted into.
Of course, if they pulled this off effectively, the drops all were probably executed soon after the 2h window, and then you've got a much colder trail to follow, even if you find one of the mules and magically have video surveillance of the region.
And then you have a 100-player Prisoner's Dilemma, unless they organized the group in a decentralized manner.
Cash flows up, risk flows down. Seems to be the MO of most organized crime.
These 100 guys aren't a part of "the group" though, they're just random idiots hoping to score a quick buck.
The people actually running this in all likelihood aren't even in japan.
His friends says, "What are you doing? You can't outrun a bear!"
His friend replies, "I don't have to outrun the bear; I only have to outrun you!"
A small crew can disappear but 100's of people at least some of them with records and known to the police not a chance.