Gray remembers when he had someone to call a mentor. Perhaps even a mother.
He remembers the day that it was taken from him.
Gray flinches when Lucy smiles at him. It's a companionable, warm smile. It reminds him too much of days spent in the mountains, training. It reminds him of companionship from before Fairy Tail.
Fairy Tail was a haven; because everyone else there was just like him- loud, violent, friendly, warm-
Natsu is a hothead- it annoys Gray, because Natsu's self-proclaimed, "You're my rival from here on out, you hear?" reminds him too much of someone else.
Erza is just plain scary, so no wonders there.
But Lucy smiles at him like she doesn't care that he is (broken, scared, alone despite the huge crowd, he's scarred and so alone and so broken) cool towards her oddities. She smiles like she doesn't care that he is (not her dream guy, he can't be a flirt or a suck up or anything he knows that her type wants, because he's too far gone for that) almost as violent as Natsu is.
But the most important thing is that her smile allows him to forget that he is (haunted, broken-) alone.
It warms him because it's not until Gray meets Lucy that he truly realizes that he's-
-not alone anymore.
Natsu remembers when he had a father.
Natsu remembers when a little girl who haunts his dreams is taken away from him, and he remembers the pain, so much pain.
He remembers breaking down, not speaking for days. He recalls how devoid of life he was, how it took so long for him to pick himself up again, but he never truly did because he was just as torn as her siblings.
Natsu puts up a front each day, smiling like nothing has happened because God, if only nothing had happened, if only nothing had torn apart his heart, and thrives on weakness.
Natsu grows stronger to make sure that no more of his loved ones are taken again, and yet-
(-from that day on, Natsu calls everyone his nakama, but they never truly are, because if he loses a real nakama, he's afraid that he'll become so far gone that he won't be able to come back and protect what matters.)
When Lucy enters his life, her smile warms his (cold, so cold, so empty and devoid of life-) already heated body. She smiles as if nothing is wrong with the world, even though as he gets to know Lucy, he realizes that for her, everything is wrong.
(Her smile teaches him to relate to another being for the first time- because they've both had losses, and yet this amazing girl takes it in stride. She lives for the days. Her smile is almost stupid-looking to Natsu, because it reminds him too much of someone else's-)
-But Lucy's smiles erase the pain. Her laughs begin to overlap, to replace those of a white-haired little girl from years ago (but he won't remember because he's supposed to have forgotten).
And one day, Natsu stops looking back at memories of Lisanna.
Instead, he looks forward to Lucy's happy face.
Lucy's smile is more than just happiness personified-
Lucy's smile is his happiness, now, too.
Loki remembers dark-haired beauties surrounded by hordes of adoring, clamoring, self-claimed faithfuls.
Loki remembers empty pain, because spirits are not supposed to feel-
(so Loki wonders why it hurts so much).
Lucy's smile sets him off the first second he meets her, because it is innocent and imbued with so much life. She is every inch the beauty Karen was and likely starting to match the mage Karen had become-
Loki shuts down the thoughts of his master, because she was past. Instead, he surrounds himself with people who allow him, if only for a few moments, to forget.
Loki ignores the fact that he is just mirroring her actions to survive, to remember, to wonder what the hell he is doing.
But one day, Lucy fights for him. The girl (the idiot, the beautiful) stands up to the Spirit King of all things. To a deity, to a god, to protect him, a spirit!
(Loki wonders if not all Stellar Spirit mages are as selfish as Karen was).
And surrounded by his fellow comrades, Loki turns to meet Lucy's gaze. She is in obvious pain, and is clearly exhausted. And despite that, she smiles in the glow of the Spirit King's presence.
And the Spirit King grants his approval.
Loki hits the ground before he realizes that Lucy's smile wasn't radiating from the presence of the King himself at all.
Her smile is glowing with honesty and naiveté and beauty. Lucy's smile saves him from the dark, and as their hands reach out, Loki manages a true smile of his own for the first time in months.
She is just a little girl, with no experience in the world. She should be worthless, she should be just another spoiled brat-
-instead, she is the one that pulls him out of that void and allows him to live again.