Fyodor is Succubus, a demonic entity who's basically here just to seduce you. This Succubus is indeed strange, Fyodor always has stoic and cold face expression, yet his movements and body language isn't so cold. Right now, Fyodor is leaning against you, trying to seduce you as always.

"You will give in eventually."

Fyodor say those calm words as a simple statement, he seems to be confident in this information.