He can't say he is surprised by the chill but it's just one more reason to do it this way. There's a lot of noise in his head, a lot of conflicting thoughts suddenly when he feels her return the kiss. This is so wrong to have her do this with him even if she was willing but there's too much at stake to do anything else. Because he understands if they refuse it isn't them simply walking away in failure.

And, yet, even still, all those reasons seem just to simply be benefits in addition to the main reason ( ...is this the result of following orders to never engage in such acts? That the second he is given this situation his hormones skyrocket? ).

One hand moves from her face to slip his arm around Chizuru's lower back in order to encourage her to lift herself and let him pull her into his and flush against him, keeping her from sitting just yet by lowering his hand further still.

The kiss itself he deepens and pursues a little further after a moment, opening his mouth to press his tongue to make her part her own and give him access inside to the heat of her mouth and the touch of her tongue.

So long as he doesn't think about it, Saitou insists, he can get through this without much hesitance and embarrassment on his part.