Sayuri (dark brown hair often tied into a ponytail) and Yuka (light brown hair) are Akane's closests female friends. It can be said that they are Akane's version of Daisuke and Hiroshi, with the exception that they don't seem to be jealous of Akane as Daisuke and Hiroshi often seem to be of Ranma.
They are always around to help cheer Akane up and give her support and often to help underscore Akane's feelings towards Ranma (usually negative feelings).
They have fairly small parts in the anime, and even smaller parts in the manga. Their screen time pales in comparison with their counterparts Daisuke and Hiroshi.
The Meaning Behind the Name
Yuka means "floor". Sayuri sounds like "sayuu" which means "influence, control, or domination." These names have no hidden meanings, they are ordinary names for two ordinary girls.
Masami Toshima & Cathy Weseluck
Masami Toshima provides Yuka's Japanese voice, and Cathy Weseluck (Shampoo) provides the English.
Yoshiko Kamei & Willow Johnson
Yoshiko Kamei is the voice of Sayuri in Japan. He other roles include Toshi Tsukikage in Tobe! Isami, Gema in Digi Charat, Tonis's Mother in Trigun and Kakipi in Mahou Shojo Neko Taruto.
Willow Johnson (Kasumi) is her English language voice.