She graduated from Morning Musume on May 7, 2005, and after five singles, V-u-den finally released their debut album, Suiteroom Number 1, in November 2005.

Ishikawa has starred in a Hamtaro movie with her Ecomoni partner, Sayumi Michishige, and soloist Aya Matsuura.

In line with Mari Yaguchi's involvement in the Japanese 2007 adaptation of the popular 1955 Broadway play, Damn Yankees, Rika was double cast with fellow 4th Generation ex-Morning Musume member Nozomi Tsuji in "When Will You Return?"

[1] In mid-2007, Ishikawa joined the Japanese idol group Ongaku Gatas along with fellow members of Gatas Brilhantes H.P.. On October 12, 2008, it was announced that she would pair with fellow ex-Morning Musume member Hitomi Yoshizawa in the new unit Hangry & Angry in collaboration with a Harajuku fashion store of the same name.

On March 13, 2017, she married a professional baseball player, Ryoma Nogami and gave birth to a baby boy in April 2018.