It's not that he doesn't want to kiss her. He really, really does, out of all the girls in Marina Miwako may be the one he'd want to kiss the most, but at the same time... he doesn't. Not like this, not when he knows what it'll do to her. His own emotions are iron-clad, hardened after years of unrequited love but she's different and by know he knows just how badly this is going to hurt her.
And so he decides to pretend. It's not easy but he's done worse things, and at least this is for the greater good. For her good.
Releasing an annoyed sigh Sanji follows her instructions, setting the box down on the ground before straightening himself up. Relaxed, nonchalant even, vaguely annoyed that they got caught but still confident that this isn't a big deal. Just another shitty trick Marina kept up its sleeve. ]
Shitty things... [A reassuring smile.] It's alright, Miss Miwako. Let's just get it over with.