As his mouth took hers in, he bargained on what her reaction could be. He made sure to do it with care and also brevity. He only wanted to know if she was softening up to him yet or not.
Also, he wanted her to know what he intended on achieving by inviting her to come into the palace with him.
All through the short moment of kissing her, she stiffened and remained like that. It showed how confused and unsure she was. It wasn't the type of reaction he needed. It meant he still had a lot to do.
Although, apart from his hands that went over her back and waist, he didn't pry any further. He made sure the kiss was as reserved and harmless as she was.
He only wanted to relay his intentions to her, using the language of a kiss. There was no reason to work this hard when he had the pill with him but he found himself not minding the extra stress of wooing her.
His urge to have her consent, to ensure she was with him on this baffled even him.