You call yourself an "Otaku" ?!!

Classmate:I love anime! I'm a proud Otaku!
Me:Me too! Kampaaai!
Classmate:Do you know the anime black butler?
Me:Yes! Kuroshitsuji right?
Classmate:Umm, Yes, My favorite is Sebastian Michaelis!
Me:Oh! Then, if Sebastian really is your favorite, Who is his' Seiyu then? :D
Classmate:What's a Seiyu?
Me:-__-