Billy is a member of the Oklahoma High School team in the Kunio-kun franchise, who first appears in Bikkuri Nekketsu Shin Kiroku! Harukanaru Kin Medal.
billy and jimmy has the exact same face and eyes of the Hattori Twins (Ryūichi and Ryūji), but he has a different hairstyle and the same "Caucasian" skin tone used by Johnny.
The character returned to the franchise in Super Dodgeball Brawlers and River City Super Sports Challenge.
River City Super Sports Challenge ~All Stars Special~ confirms that this Billy character is Billy Lee from the Double Dragon franchise (this was not confirmed when the character debuted). In this game, Billy is a palette swap of Ryūichi with lower stats. The Hattori twins have black hair, while Billy and his brother Jimmy have brown and blond hair respectively (this is the first official game in the Kunio-kun franchise in which Billy Lee makes an appearance as a playable character).
Billy returns as part of the World Team in River City Melee: Battle Royal Special and River City Melee Mach!!.