On/Off (stylized as ON/OFF) is a Japanese Jpop duo which consists of twin brothers, Naoya Sakamoto (坂本 直弥, Sakamoto Naoya) and Kazuya Sakamoto (坂本 和弥, Sakamoto Kazuya). The duo debuted in 2007 releasing the single "Eien no Setsuna" (永遠の刹那, "Eternal Moment").
On/Off debuted on November 21, 2007 with "Eien no Setsuna" (永遠の刹那, "Eternal Bond"), which was used as the ending theme song the live-action adaptation of Fūma no Kojirō; they were also a part of its cast. The single debuted at number 59 on the Oricon charts. Following the release of "Eien no Setsuna" was their second single "Futatsu no Kodō to Akai Tsumi" (ふたつの鼓動と赤い罪, "Two Beats and a Red Sin") on June 4, 2008. The single achieved more success than their debut single charting at number 19 on the charts. "Futatsu no Kodō to Akai Tsumi" was used as the opening theme song for the first season of anime series Vampire Knight. The duo released two singles, "Rinne: Rondo" (輪廻－ロンド－, "Cycle: Rondo") (October 2008) that became the opening of the second season anime of Vampire Knight and "Hana Kagari" (花篝－ハナカガリ－, "Hanakagari: Bamboo Flower") (March 2009), before releasing their debut album Legend of Twins I: Futago Densetsu (Legend of Twins I－双子伝説－, Legend of Twins I: The Legend Twins) on April 22, 2009. The former charted at number 18 on the charts and was used as the opening for the second season of Vampire Knight; while the latter failed to chart on the Top 30. Their single "Butterfly" was also used in the anime Durarara!! as the ending theme song. Their new singles "Hajimaru no wa, Sayonara" was used as second opening for anime series Beelzebub and was composed and produced by popular J-pop artist Daisuke Asakura. On 2/11/11 they release their new single 'Akatsuki' and on 7/12/11 is the release of their new album 'Legend of Twins II : Zoku Futago Densetsu'