I liked the voice of the default menu navigator character, Linka, so I took a look in the credits. It's Jenny Shima, Cyber Diva's VP!
This game rules by the way. I enjoy almost all of the music, and the charts are really well done. The visuals are exciting but can be a bit much at times with all the flashing. It's fun to chip away at the missions and unlock things. The first Vocaloid Pack and the Undertale DLC are excellent, but now the total cost is getting a bit high since I know I'll have to get the second Vocaloid Pack when it drops in North America. The base game has enough to keep you occupied for a long time though if you can resist the DLC.