"OSCA" is a song by Japanese rock band Tokyo Jihen, led by musician Ringo Sheena. It was released as the band's fourth single on July 11, 2007, as one of the two singles before the band's third album Variety (2007). It was the first and only single released by the band that did not feature writing by vocalist Sheena, instead created by the band's second guitarist, Ukigumo.

Vocalist Ringo Sheena originally debuted as a solo musician in 1998, however decided to become a member of a band instead for her main musical activities, and debuted Tokyo Jihen in 2004. After their debut album Kyōiku, two of the original members of the band made decisions to leave, and were replaced by pianist Ichiyo Izawa and guitarist Ukigumo. The new line-up released the single "Shuraba", a song used as the theme song for the drama Ōoku: Hana no Ran., and the band's second album, Adult (2006). Adult, while featuring lyrics entirely written by Sheena and the band collaborating to arrange the songs, also featured "Himitsu", which was arranged solely by Izawa, and "Tegami", which was composed by Izawa and arranged by Sheena.

In late 2006 and 2007, Sheena briefly resumed solo activities in collaboration with Neko Saito, on Heisei Fūzoku (2007), a soundtrack album for the Mika Ninagawa film Sakuran. The "OSCA" single was first announced on May 17, 2007.

The Variety project for the band involved the band members other than Sheena amassing demo tapes, and the band making careful selections. For the project, Sheena worked as a vocalist and a lyricist. After the band's tour for Adult, Domestic! Just Can't Help It, finished on May 30, 2006, Sheena requested band members Ukigumo and Ichiyo Izawa write songs for the band's next studio album. While Sheena is the primary songwriter for her solo career and for Tokyo Jihen's first two albums, she occasionally goes through periods of not being able to write music.

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