The original Street Fighter opponent who is described as an expelled Shorinji Kempo instructor is Retsu.
Retsu is one of the first game's eight regular computer-controlled challengers. He represents Japan, alongside Geki, and appears before the player travels to the United States, China, Great Britain, and Thailand. His martial-arts background helps distinguish him from the other early opponents, whose profiles include a ninja, a boxer, and a Chinese martial artist.
A common mix-up is confusing Retsu with Geki. Geki is the Japanese opponent associated with a tekko-kagi, a claw-like weapon, while Retsu is the instructor expelled from his school. Retsu is also easy to overlook because the 1987 game makes only Ryu and Ken normally playable; the other fighters are opponents rather than selectable tournament characters.
The original Street Fighter was released in arcades in 1987 and introduced the international tournament structure that later games greatly expanded. Its ten-opponent route included eight regular challengers followed by Adon and Sagat in Thailand.