I'm not sure I think it's rape. I mean technically and legally (according to laws in our world) it is. He never consented, but he was never entirely unwilling either. His thoughts in ch.1 were getting lewd, ch.2 "There's a proper order for everything". And he was never really that upset after the deed until this chapter, and then more for the death-threats. He's in a messed up situation, but isn't protesting that hard in his mind.
I'm probably a horrible person for thinking so.