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.
[9] On August 1, 2012, D-Unit released their first album "Welcome To Business" and their first music video for their debut single "I'm Missin' You".
Before debut, D-Business confirmed that the group will increase and decrease the number of members at different times.
On February 10, a teaser was released which announced Zico of Block B composed and produced the title track.
"[15] In May, it was announced RAM would be filming a reality show with sister Boram of T-ARA and her father.
To commemorate the group's first anniversary in August, a remix of "Before the Weekend Comes" from the first studio album was released.
Also in September, RAM and Z.I.N performed in Vancouver, British Columbia for the "2K13 Feel Korea Festival".