Sanpei made her voice acting debut in the anime series UFO Baby.

In 2006, she played the first female role in the series Ouran High School Host Club as Shiori Ebisugawa and, in 2007, she voiced Nozomi Yumehara/Cure Dream in Yes!

After leaving the theater company Wakakusa around May 2007, she went to Production Baobab on November 1 of the same year after a freelance period.

In 2010, she joined the stage after a long time for the performance of Song of Joy.

On October 1, 2011, she left Production Baobab to transfer to the Axlone agency.