[He successfully fights the natural instinct to tug his shirt down once it starts to come undone, in part because he's actively trying not to and in part because so much of his concentration melts away at just feeling her pressed so close against him. All of her, soft curves and dizzying warmth, chest rising and falling against him with each breath.
It's better than he could've ever imagined, enough so that he finds courage to slide the hand on her back higher up, while the other shifts back to nest in her hair. Following the ridge of her spine he moves his hand up until it comes to a rest between her shoulderblades, palm pressed against the clasp of her bra and if his heart wasn't already beating so hard, it would be by now. ]