Kansai (関西) is the second most populous region in Japan behind its eastern neighbour Kanto. The two regions have a so-called "East-West" rivalry, which is a major driving force behind the main plot of the Yakuza series. Chiefly, this rivalry is reflected in the repeated power struggles between Kanto's Tojo Clan and Kansai's Omi Alliance to become the largest yakuza organization in Japan.
Kansai is known for its unique Kansaiben dialect, which is spoken by many Kansai-native Yakuza series characters such as Goro Majima and Kaoru Sayama, the latter of whom hides it when she is in Tokyo due to feelings of inferiority.
The East-West rivalry between Kansai and Kanto stretches back centuries. The Kansai city of Kyoto was the seat of the Japanese emperor, and thus the capital of Japan. This changed in the Edo period, so called because the emperor was forced into exile in the Kanto city of Edo. The beginning and end of the Edo period form the settings of Ryu ga Gotoku Kenzan! and Ryu ga Gotoku Ishin! respectively.