AN: Could also be titled, "Three Times Emma Kisses Killian and One Time They Kiss Each Other".
The first time (which isn't really the first, chronologically-speaking) it's like bursting into flames. It's teeth and tongues and ferocity, and because Emma Swan doesn't do anything halfway, the kiss lasts longer than either of them expect it to. And she feels her head reeling with a pleasant dizziness, and her palms start to sweat, and her heart wants so badly to leap out of her chest but she's determined not to let it.
Then it's over, both too soon and not soon enough, and Emma gains her composure before Hook can see her shaking hands, her unsteady legs. Then she's marching away, everything already forgotten, except that she's smiling, except that Emma knows she'll relive the memory in her sleep.
/
The second time, it's not exactly a kiss, but it still leaves Emma breathless. Her hands shake again, out of fear this time, and she's pleading with him, his real name spilling from her mouth, and all she can register is the panic that sets deep in her chest. And she knows this is all so bad, that there will be hell to pay for the choice she's made.
But Emma can't bring herself to regret her sacrifice, because even as she feels her magic being drained away, she feels Killian startle back to consciousness; when his eyes open to hers, suddenly Emma can breathe again.
/
The third time (which is actually the first), it's not really him. It's not Killian hanging on her lips, but Hook, and even though Emma knows it she's putting all of her into the kiss, anyway. He's got the same smile as Killian and his eyes, though they hold more sadness, are just as blue. His hand grips her just as tightly, if a little carelessly, and Emma knows it's not him, but she's leaning backwards from the force of his lips, pulling him along-
And then it is Killian, the real Killian, looking at her with a fire in his eyes, and suddenly Emma's falling, though it has nothing to do with the way the ship lurches beneath them.
/
The fourth time, it's everything all at once. It's gratitude as much as it's apology, relief and care and worry tucked into the thumb he presses to her chin. And they're outside, where anyone could see them, but they don't care, not at all, not even a little.
For the first time, it's compromise, because it had only ever been Emma kissing him, but now they find themselves meeting halfway. It feels new to Emma, because she's finally seeing him in a new light, finally realizing just how far they've come since their first kiss. (If they were normal, Emma thinks, this could have been their first kiss; at a diner- at the end of a date, maybe- with no time traveling or missing years or pirate ships, just the moon and stars and them).
But she likes not being normal if this is the payoff, and when they part for just a moment, Emma can't help but smile.
At that moment, Killian looks at her, and the light in Emma's eyes tells him he made the right decision. He knows, in that moment, when someday she inevitably asks if he regrets trading his ship, the answer will be a resounding no. Killian no longer needed the Jolly to be his home; he found a new one in the edges of Emma's smile.