Momoko joined Hello! Project in 2002 at the age of 10 with the other 15 Hello! Project Kids. In 2004 Berryz Kobo was created, and Momoko was selected as one of the group’s lead vocalists. In the same year she was a member of Little Gatas, an official Hello! Project futsal team where the members are made up fom Berryz Kobo and °C-ute and is now a reserve member for Gatas Brilhantes H.P.
In 2007 she was selected together with °C-ute member Airi Suzuki, and fellow Berryz Kobo member Miyabi Natsuyaki for the Hello! Project sub-group Buono! , which mainly produced opening and ending songs for the Anime Shugo Chara!, but has now gone on to release more singles. Momoko was named as the official leader of Buono! in 2010, although she already self-proclaimed that before. Berryz Kobo held a concert in Saitama Super Arena for first time in 2007 and it's also the first time that Momoko sang a solo.
She interpreted Koi wa Hipparidako, which is part of their first album: 1st Chou Berryz. For her 4th Photobook "momochiiii", she held a handshake event on August 31, 2009, which made her the first Berryz Kobo member to do that (and the third among Hello! Project Kids).