D-Unit (Korean: 디유닛) was a South Korean girl group under the label D-Business Entertainment. The groups concept includes the addition of a new member with every promotion cycle. The group debuted as a trio consisting of Ram, UJin and Zin with a full-length album, featuring the title track "I’m Missin’ You" on August 1, 2012. This was followed by their debut stage on August 2, 2012 on M!Countdown. In March 2013, D-UNIT added their first guest member, JNey, a member of GP Basic.
On July 2, 2012, D-Unit released their first teaser of "I'm Missin' You" which featured member UJin. On July 4, 2012, D-Business Entertainment officially stated that the group would be holding a fan signing in Japan before the group would make their Korean debut. On July 10, 2012, the group released their second teaser which featured member Ram. On July 16, 2012, D-Business Entertainment stated that the group would show their debut progress to fans through a reality TV show called "Welcome to D-Unit" and would air on July 18, 2012. On July 29, 2012, the group released an official teaser which would feature all three members. The following day on July 30, 2012, the group released an extended 1 minute teaser.