Saito is an emotionless robot under the familiar spell. He's locked into the emotional state of when he was summoned which was bemused curiosity. Hence why he'll rush into situations which might mean certain death, since he's not physically able to feel scared, happy, or sad. He also has the slave mentality towards louise, so he can't do anything which would put her in danger or go against one of her direct orders. "Oh I could go sleep in one of the other rooms but instead I'll sleep on this bail of hay as ordered. Oh I could use this plane to escape but my master is in danger."
What's her name, the blonde girl, removes the familiar spell on saito in the novels and he breaks down into an emotional wreck, remembering his lost family, friends.
Saito's not brave or oblivious to the various females in the world, he's just lobotomized into being a smirking zombie.