In January 2006, Akimoto let Mariko Shinoda join the group without passing audition, after she won a popularity vote by fans, although she was working as a waitress at the Theater Cafe after she failed to pass the first audition back then.
AKB48 released its debut single "Sakura no Hanabiratachi" in February 2006, which made it to #10 on the Oricon weekly charts and sold 22,011 units in its first week – surprising for a group on an indie label.
On March 1 AKB48 released their first photo book, Micchaku! "AKB48" ~Shashinshuu Vol.1 the DEBUT. On March 31 Usami Yuki graduates, becoming the first member to do so.
From April 1, 2006, Team K begins performances at the theater.
On June 7 they release their second indies single Skirt, Hirari, and sang their song first time on TV programs, Music Station and Music Fighter, on June 9, and on the 17th Ayako Uemura graduates.
In August 2006, they signed a major label contract with DefStar Records, a part of Sony Music Entertainment. Their first single under DefSTAR Records, Aitakatta, was released on October 25, 2006 and got to #12 on the Oricon weekly single charts.
In October 2006, a new audition was announced to form Team B, resulting in the arrival of 13 new members in December 2006.
On November 3 & 4, 2006, AKB48 performs in their first concert AKB48 First Concert "Aitakatta ~Hashira wa Nai ze!~ at Nippon Seinenkan in Sendagaya, Shinjuku.
In December 2006, the first change was made to the three teams; transferring Kazumi Urano, Shiho Watanabe, and Natsumi Hirajima from Team A to Team B as supporting members. Ayumi Orii graduated from the group shortly after this, though appeared in the unit Crayon Friends from AKB48 after her graduation.