Well obviously instead of candy, there's something better for her to be sucking.
'Why DID it work', though? Well I'll tell you why. The power of sweet Vanilla loving, that's what. She may like licking and sucking, but not so much the very act, but probably because it's him. Yes I do so love my sweet Vanilla Osananajimi releases.
Great ending though. He's essentially come full circle. As a foolish kid, he used candy to distract her from licking and sucking on him all over, and now he's done the opposite.
And it seems like from now on she won't even need candy, because lovers don't need any reason to be...affectionate with each other.