I know posting related to Fate Extra in here is not very good idea but....
Spoiler:
Here the info according to Famitsu:
Karna (Lancer) voiced by Koji Yusa & Jineko (Master, who is net addict) voiced by Aoi Yuuki.
Lancer (described as a “mysterious servant” who is pink succubus) voiced by Rumi Okubo.