"Mach" is a song by South Korean girl groupRainbow. The song was released on October 20, 2010, and was later included on their second mini albumSo Girls. The song is also the group's second Japanese single. It was released on December 7, 2011 in 4 different versions: 3 limited editions (CD+DVD, CD + 28-pages photobook and CD Only + Bonus track) and a regular edition.
The song debuted at number 38 in the first week and climbed to the number 19 on the following week, which is currently the highest peak of the song. The song ranked at number 193 on Gaon's Yearly chart with 216,200,537 points and with 925,573 digital copies sold.
The Japanese version follows the same concept of the Korean version. A teaser of the music video was released on November 15, 2011 on Universal Music Japan's YouTube account. The full music video premiered on November 21 on the TV station Space Shower TV.
The Japanese version of the song was written by Natsumi Watanabe, Yu Shimoji and NICE73. The B-side is a Japanese version of the song "Not Your Girl", previously released in Korean, on their debut EP Gossip Girl.