"While making the first and second games in the series, I went drinking in Kabukicho with (Toshihiro) Nagoshi, the overall producer of the franchise, two or three nights every week," says Masayoshi Kikuchi, a veteran producer at Sega, as we discuss the latest entries in his smash-hit series "Ryu ga Gotoku" — known in the West simply as "Yakuza."

It might sound as though Kikuchi and Nagoshi were playing truant on those drinking excursions, but no: This was research. The gangster underworld portrayed so convincingly in the "Ryu ga Gotoku" titles is based almost entirely in Kamurocho, a fictional version of Kabukicho. So carefully modeled is Kamurocho on Tokyo's premier red-light district, located in the heart of Shinjuku, that real-life visitors may not need the on-screen map.

"Kabukicho's within an hour of our development office, so we could easily go down there to take videos or photos for each game, and we went fairly frequently," explains Kikuchi. "I basically grew up around Kabukicho, because my school was near there. I hung out there a lot as a student."