time frame: somewhere between the end of the manga and the 100 year quest
Lucy came into the apartment, flipping through the mail. She didn't even react when she found Natsu lounging on her couch, casually skimming through a magazine that published one of her more recent articles.
Natsu stood; now that she was back, it meant they can go to the guild like they planned. He casually picked up his used plastic novelty cup. It had some cheesy dragon design on it, along with the logo of the chain restaurant they found it in during one of their missions. Natsu loved it because "it looks just like Igneel, Luce!" which meant it was destined to spend the rest of its life in her cupboard.
The blonde didn't even glance up from whatever bill is in her hand when she spoke, following him into the kitchen before leaning against the counter next to the kitchen sink.
"I promised Mira I'd show her this new recipe I found. Can we stop at the market on our way?"
He grinned, excited at the idea of being her and Mira's taste tester.
"I think I can manage that," he replied easily as he leaned past her to put his cup on the counter she rested against, steadying himself with a hand on her waist - though, really, it's more as an excuse to touch her than him actually needing the help to stay balanced.
He lingered there, taking longer than necessary so he can spend a few more moments basking in her closeness. Even if she's distracted by the paper in her hand, the way she unconsciously moved closer to him warmed his heart in a way his fire never could.
"Thanks, Natsu," she says, still reading. Without even thinking about it, she presses up on her toes to casually brush her lips against his.
Immediately, the young man jerked back a step, dropping his cup, and it isn't until it clattered against the counter that Lucy was pulled from her thoughts enough to realize what just happened.
They stood there in shocked silence for a moment just staring at each other. Blushes explode onto their faces.
Lucy's mind immediately starts going a mile a minute. Sure, they had been a lot more affectionate these past few months, what with them always touching in some way - either of them grabbing the other's hands, Natsu winding an arm around her shoulders, or her increasing liberalness with cheek kisses. And, yeah, when combined with the fact that they had already promised to be together forever, this honestly seemed like the only possible outcome. But then... They had been teetering on the edge of this for years, so there must have been some reason they hadn't already fallen over it, right? Was this possible? Were they even ready for this? Oh, Gods, did he even want this - did he even want her -
Natsu's brain had a much simpler reaction. He merely studied her carefully for a moment to make sure she wasn't about to attack him and, when it seems safe, steps right back into her personal space.
He huffed out a breathy laugh at the look of impending doom on Lucy's face. Instead of speaking, he took her face into his hands, mumbled something that sounded suspiciously like "finally," and brought his lips down onto hers.
It isn't until later that they remember their plans for going to the guild. They both quickly agree that Mira can learn about that recipe tomorrow.
... Or maybe the day after that.