Yakyuken (野球拳?) is now widely known as a Japanese strip game variation of rock–paper–scissors wherein the loser of each round removes an article of clothing, similar to strip poker. Yakyuken gets its name from a Shikoku chant associated with the non-erotic version of the game which is still a local performance art today. It became a part of culture in Japan due to mass media influence, and in other Asian countries after the influence of TV variety shows and Soft On Demand. Numerous hentai games have been made featuring the Yakyuken gameplay, and several American studios, such as Lost Bets Productions, focus on the filming and marketing of Yakyuken and other related strip games.
The term initially originated from a Shikoku baseball game in October 1924, between the local teams of Ehime and Kagawa. The Ehime team lost the game 0-6, and its manager, senryū poet Goken Maeda (前田伍健), improvized a cheerleading dance from the tune of classical kabuki Botan ni Chōougi no irodori (牡丹蝶扇彩) to boost the morale of his humiliated team. This dance later became an iconic feature of the Ehime team.
In 1954, singers like Ichiro Wakahara (若原一郎) and Terukiku (照菊) from King, Yukie Satoshi (久保幸江) and Kubo Takakura (高倉敏) from Nippon Columbia, and Aoki Harumi (青木はるみ) from Victor Japan each adapted the dance and its lyrics into record singles named Yakyuken (lit. "baseball fist"), and the term quickly became known nationwide. In 1966, the city of Matsuyama, where the cheerleading dance originated, introduced it as a representative taiko dance for Matsuyama in Shikoku's annual August banquet. In 1970, the banquet dance was transformed into the more popular sansukumi-ken parlour game that continued to today, which the Matsuyama people regarded as Honke (lit. "senior branch" or "orthodox") Yakyuken.
Strip sansukumi-ken, however, had been a popular activity in the Japanese red-light district since late Edo period. In 1969, Nippon TV introduced a skit as part of its hugely popular owarai variety show Conte #55's Counterprogram Strikes! (コント55号の裏番組をぶっとばせ!) by comedians Kinichi Hagimoto and Jirō Sakagami, where beautiful female guests were invited to play sansukumi-ken on stage, and the loser would undress and auction off her clothes to the studio audience for charity. This skit was successful enough in terms of ratings that later in the year it became its own separate show called Conte #55's Yakyuken!! (コント55号の野球ケン!!), named as Hagimoto was a keen baseball fan. The rating success of the show gave the audience a misconception that Yakyuken was related to strip games, which led to its more well-recognized modern misconnotation. Because of this, Hagimoto himself personally visited Matsuyama in 2005 and apologized to Sawada Tsuyoshitoshi (澤田剛年), the fourth-generation iemoto of Honke Yakyuken, for unintentionally distorting the definition of Yakyuken.
The erotic misconnotation of the word "Yakyuken" was further propagated by the prolific Japanese pornographic industry, as strip games and sexual intercourses involving the Yakyuken chant were frequently depicted in adult videos. This led to the misconnotation becoming well-known in other countries where Japanese pornographic productions enjoy significant popularity. Yakyuken eroges are also popular in Japan and many East Asian countries, with first Yakyuken video game created by Hudson Soft for the Sharp MZ-80K in 1981.[unreliable source?]
- edepot (2013-04-09). "First Adult Video Game: Yakyuken (ハドソン 野球拳 1981)". YouTube. Retrieved 2013-04-26.