Behold! My inability to write a in a linear fashion. To the fandom gift you with more Percy and Jack goodness. Merry Christmas all!
Disclaimer: Still not owning these characters. Belong to their respective creators and the people who hold the rights.
Jack Frost thinks he's been around a long, long time.
He hasn't, actually, in the grand scheme of things 300 is young for an immortal but he doesn't know that. But 300 years is a long time to be alone and isolated.
That's why he's so surprised when he hears, "Hello?"
Jack studies the boy in front of him, all black, blue, green and white, from the safe distance of his tree and pretends he isn't panicking. After all, isn't this what he wants? To be seen, to be acknowledged?
The boy on the ground looks up at him, perplexed. Jack thinks he looks strange, blue shimmering wings, and blue and green pants and tunic combination with a opalescent sash just to add some contrast. Longish black hair done up in a braid, bangs sweeping across his sea green eyes, fit and tan with a bronze sword strapped to his back the way Jack sometimes carries his staff.
"You can see me?" he asks, afraid of the answer.
The boy nods. Jack jumps up in jubilation and shouts his happiness to the world.
It's the beginning of a beautiful friendship.
"I just want someone to believe in me, you know?" Jack looks over at his friend, certain he'll understand, as Percy's rarely seen either.
Percy makes it a habit to surprise him though, so when he replies, "Maybe before someone believes in you, you first have to believe in yourself." Jack doesn't know what to say to that, so he flies off, feeling angry and empty, and maybe a bit betrayed and ignoring that voice in the back of his head says, maybe Percy is right.
They don't speak for another 3 years.
When the battle with Pitch has come and gone, when Jack has officially been made a Guardian – The Guardian of Fun, in fact - and the celebration is winding down, he remembers Percy.
Camp Half-Blood tends to be overlooked by the Guardians. Not because they don't care about the children there, but because by the time a demigod reaches camp they aren't really considered a child anymore.
Also, Immortals tend to get a bit territorial and campers don't really believe anything else exists beyond the Greek canon that they have to memorize to stay alive.
Slowly, Perseus and Jack Frost are changing that.
The rest of the Guardians don't actually meet Percy until much later, interrupting what was, even by the standards of the twosome, an EPIC sparring match, snow and sleet flying every which way, starlight and frostlight whipping through the winds, the clash of sword on staff.
Of course the Guardians immediately misinterpret it, thinking this strange winged warrior is threatening their winter child.
(Percy smirks when he realizes this later, that Jack doesn't realize he's managed to acquire a family and all the things good and bad and just plain annoying that go along with that. Even later he realized the Guardians have neglected to mention this fact to his snowy friend.)
They eventually get it sorted out. But in the meantime it is a good thing that Perseus is such a skilled warrior.
(Between dodging Toothfairies and arrow feathers, exploding eggs and boomerangs, dueling the large Russian with two swords and avoiding those tendrils of dreamsand while Jack is flying around and yelling trying to get them to stop, Perseus wonders why it feels so familiar to be hopelessly outnumbered and outgunned, though.)
North can't find Percy on his lists, Naughty or Nice.
Bunny can't ever remember hiding eggs for him.
Sandy's dreamsand doesn't really work on him.
To Jack, all this seems terribly depressing and unfair.
Percy just thinks it makes sense. He may not remember his mortal life very well, but he knows he doesn't belong to the Guardians like Jack does.
He's strangely okay with that.
His family is elsewhere.
"I think I was a demigod, when I was alive." Percy states, seemingly out of thin air.
Jack looks at him, aware this has bugged his friend since they raided Tooth Palace and came up empty-handed. Toothiana doesn't have his baby teeth (which she considered a terrible oversight and was so apologetic Jack had to pull her off his friend and explain Percy didn't really mind, not like he had.)
"Maybe you were. It would make sense, all things considered." And really, who better to guard the demigods then one of their own, who knew and understood what living that life is like?
Jack still can't understand how the Olympians can doom their children to live this kind of half-life.
"There's a Cabin up the coast from here. I think it's my home." Percy says again, unsure and a little scared.
Jack thinks about the older, black-haired spirit-god he'd seen with the youngest campers, thinks about how he seems to look behind them every time one makes it safely across the boundary, as if expecting a companion to run in behind them and thinks 'oh.'
He extends his hand to Percy, "Let's go find out then."
Percy takes his hand and the two troublemakers fly off towards a stretch of beach Percy has always felt at home in, much like Jack's Lake in Burgess.
Percy isn't going to find his answers by just sitting around, Jack knows that much.