Pachinko is a pinball-like slot machine game. It is officially not considered gambling because Japanese laws regard pachinko as an exception to the criminal code on gambling for historical, monetary, and cultural reasons. Pachinko parlours can be found all over Japan, and they are operated by private companies. As of 2011, there are about 12,480 pachinko parlours in Japan.
In pachinko, when a player's ball makes it into a special hole to activate the slot machine and a jackpot is made, they are rewarded with more balls. Players can then exchange the balls for prizes of different value at a booth in the parlour. Money cannot be awarded at pachinko parlors as this would be in violation of the criminal code. However, players almost always exchange pachinko balls for special tokens, usually slits of gold encased in plastic, and then "sell" them at a neighboring shop for cash. Usually such shops are also owned by the parlor operators, but as long as the winners don't get cash in the parlour, the law is not broken.
Japan has long been known for its maid cafes. In Akihabara, Tokyo there is what resembles an office but is called a Maid Casino. It is a casino and all the staff are dressed as maids however in our opinion it resembles more like school children.
How does it work? They have different tiers, but you can enter for as cheap as 2000 yen and they give you $200 in chips. From there you get a complimentary drink and you pick your game.
After every hour or so you have to pay a small fee (in chips) to stay. If you get bored before going bankrupt, you can show the staff how many chips you have and they will keep track for next time. You will still have to pay a small fee to enter when you come back, but it is much cheaper than the initial cost.
At blackjack they call the numbers out in English, and when someone hits and gets a 20 or 21, everyone says ナイスアップ (Nice Up!).
The dealers tend to have the same skills as a bad casino trainee but no one seems to mind.
Unfortunately, maid-themed anything in Japan attracts the weirdest of the weird. This maid casino is usually full of Otaku (nerds).
Yakuza are known to operate illegal casinos in Japan. In addition to traditional casino games, Mahjong can be played for money and many mahjong parlors have ties with the Yakuza to assist collecting debt from players who default.
Another illegal gambling opportunity is offered by mobile gambling sites. At these sites, Japanese gamblers can play rock-scissors-paper and win cash prizes. In 2010, the owner of one of these sites was arrested and confessed of earning over $1 million. The punters were offered to purchase betting tickets for ¥315. They could get ¥1,000 if they won no less than 3 times in a row. ¥10,000 was the prize for those who won 5 times in a row.