In late 2006, Kikkawa auditioned for the eighth generation of Hello! Project's main group, Morning Musume. She was one of the six finalists, but lost to Aika Mitsui in the end.
On April 7, 2007, Hello! Project's official site listed her as a member of Hello Pro Egg. On April 30, 2008, she had her CD debut as a member of the unit MilkyWay for the TV anime Kirarin Revolution.
On January 2, 2011, Kikkawa made her solo live debut as the opening act of the 2011 Hello Project winter tour. Her debut song is titled "Sayonara Namida", and she has since gone on to perform two other new songs, "Candy Pop" and "Fuyuzora Hanabi".
In 2013, Yuu was recruited to join a unit with the duo Kimaguren in order to promote Glico's new coffee brand Café-ole. They are under Universal Music Japan.