
Quick answer — Naoko Takano voices Kohaku in Carnival Phantasm, Megumi Reinard in Martian Successor Nadesico, Magical Ruby in Fate/kaleid liner Prisma☆Illya and 2 more characters.
Naoko Takano voices Kohaku (Carnival Phantasm), Megumi Reinard (Martian Successor Nadesico), Magical Ruby (Fate/kaleid liner Prisma☆Illya), Midori Tooyama (Brighter Than the Dawning Blue), Takae (The Devil Lady).
Kohaku is voiced in Japanese by Naoko Takano.