In 2009, Iikubo Haruna won a special award at the exclusive auditions for the fashion magazine Love Berry. She first appeared as a model in the June number of the magazine. Since the July issue, Haruna Iikubo adopted the stage name Hau Dan (壇 はう). She "graduated" from Love Berry (left the project) in the February 2011 number.
Iikubo was selected from Morning Musume's 10th Generation audition to join the group on September 29, 2011, along with Ishida Ayumi, Sato Masaki, and former Hello! Pro Kenshuusei Kudo Haruka.
The tenth generation made their official presentation on the same day they were announced as new members in the "Morning Musume Concert Tour 2011 Aki Ai Believe ~Takahashi Ai Graduation Memory Special~" concert, and they participated in a performance of the song "Tomo". They also participated in the end of the song "Namidacchi".
On April 18 2012, it was announced that Morning Musume's Tanaka Reina and the 9th & 10th Generation members will participate in a new stage play titled Stacey’s Shoujo Saisatsu Kageki. The musical runned from June 6-12.
On July 20, 2012, it was announced that Iikubo, Yajima Maimi, Tokunaga Chinami, Natsuyaki Miyabi and Nakajima Saki were chosen to form the unit DIY♡.
On July 27, 2012, it was announced that Iikubo will change her Morning Musume color. Her new color, Honey Yellow, was revealed in a Ustream show on July 30, 2012.