[csa]

The illegal parlors exist, just like illegal private poker games exist in the US.

I’m not sure about numbers, but I know many people in Japan who play mahjong with community friends just like I know many people in the US who have poker home games.

I have played both games in the casual community games, and they are generally very friendly even though money is involved. Typically, the amount wagered is “in the budget”, skill sets are usually in the same neighborhood, and ringers either self-moderate their winnings (this is me in poker and a friend of mine in mahjong) or get uninvited.