On January 2, 2011 at the first Hello! Project 2011 Winter ~Kangei Shinsen Matsuri~ concert Tsunku announced Ikuta as one of the new members of Morning Musume's ninth generation, she joined alongside Fukumura Mizuki, Sayashi Riho, and Suzuki Kanon.
The ninth generation made their concert debut the same day, participating in the song "Tomo".
Ikuta's debut single in Morning Musume is titled "Maji desu ka Ska!"
On June 12th, 2011, Ikuta's first e-Hello DVD was announced; "Greeting Ikuta Erina" set to be released July 2nd, 2011.
On July 30, 2011 Ikuta cut her hair very short.
It was annouced that she replaced Ogawa Saki on Oha Star.
On March 27, 2012, she graduated from Oha Star and Oha Girl Maple.
On April 18, it was announcced that Tanaka Reina and Morning Musume's 9th & 10th Generation members will star in a new stage play titled Stacey’s Shoujo Saisatsu Kageki. The musical will run from June 6-12.
On July 4, Ikuta Erina annonced, on her Ustream show, that she will change her official member colour from Dark Purple to Light Green in the fall.