The status of online casinos in Japan exists in something of a gray area, with the practice of taking part in online casino action being illegal but not something that results in much attention from the authorities. This means that a great many Japanese players use online casinos and primarily do so via online casinos that are based overseas.
The casino in Japan market is dominated by online slots, and the Japanese have tastes that steer towards the more enigmatic slot titles, looking for those that have a story behind them and unsurprisingly are big fans of those with an anime theme.