The loveable Osaka's voice is provided by Yuki Matsuoka. You can visit her offical site here: http://www.d-koen.com/myuki for more information and pictures.

Yuki's other voice work include the following:

"Tennen shôjo Man" (1999) (mini) TV Series
(aka "Man, a Natural Girl" (Japan: English title))
"Oja majô doremi" (1999) TV Series .... Aiko Senoo

This information was acquired from the Internet Movie Database (IMDb)