In 2008, AKB48 producer Yasushi Akimoto decided to create a "Saturday Night 48" show, based on the concept of an "Adult idol" that would perform every Saturday at 10 pm. The shows were restricted to fans aged 18 and older. He also wanted to differentiate from AKB48's usual uniforms with sexier attire. In July 2009, two AKB48 members, Megumi Ohori and Kayo Noro were chosen as the first two members of the group. At the same time auditions were held to find other members. The SDN48 debut stage Yūwaku no Garter was held on July 25. At the end of AKB48's three-day Nippon Budokan concert the teams were reshuffled, leading to the removal of Kayo Noro, Megumi Ohori, Yukari Sato, and Kazumi Urano, leaving them to focus solely on SDN48 activities. Noro was also made the captain of the group. It was announced on September 27, 2009, that understudy Yuki Iwata had departed from the group due to health reasons. Two months later, Eiko Maeda was transferred from sister groupSKE48 to SDN48. Upon joining the group Maeda changed her stage name to Machiko Tezuka.
During their first anniversary concert, Noro announced to the audience that SDN48 would debut under Universal Music in the fall. The group also suggested they would be eliminating the age restriction. Through their TV show, Suppon no Onna-tachi, SDN48 held a senbatsu election to determine the top twelve members who would participate in their debut single. Former AKB48 member Megumi Ohori won No. 1 and was given the center position. The single would be titled "Gagaga" and be released on November 24, 2010. On September 30, 2nd generation member Sakura Fukuyama announced through her blog that she would be leaving the group due to health problems. Chinese member Chen Qu was chosen as Fukuyama replacement. The group was scheduled to release their second single "Ai, Juseyo" on 23 March 2011; however, due to the Tōhoku earthquake and tsunami on 11 March, the single was postponed until 6 April.
2012: Disbandment
On March 31, 2012, all the members graduated from the group and the group was disbanded. On April 19, 2012, former SDN48 members participated in AKB48's 2nd revival stage concert which took place on May 15.
2013: Reunion & New Projects
On March 31, 2013, one year after the disbandment, an SDN48 reunion concert was held at AKB48 theater. On May 6, 2013, it was announced that seven former members were creating a new group, called 7cm. The group was under the Avex label and the members include Juri Kaida, KONAN, Mana Ito, Haruka Umeda, Megumi Imayoshi, Mami Kato and Miyuu Hosoda. The group disbanded in December 30, 2014.
All SDN48's members did perform only one stage, "Yuuwaku no Garter". They usually were divided as 1st and 2nd/3rd generation stages. They performed at the AKB Theater.
