Percy and you have been dating for four months when he disappeared, but you've known each other since you were, what, thirteen?
The weeks you spent not knowing where he was felt terrible, but you ended up finding your way back to each other.
Turns out that Hera had erased all of his memories and he ended up at Camp Jupiter, a place for the sons and daughters of Roman gods and goddesses. Surprisingly, there was one thing the demigod could remember of: your name.
He knew for sure that name meant something and that the girl to whom it belonged was his girlfriend.
When you two reunited after so long, Percy's memories were gradually returning. You couldn't help but feel a pang of jealousy in your chest when you saw him at Camp Jupiter, with new people, 'cause what if those other campists had replaced his friends at Camp Half-Blood? What if he didn't want to come home?
But he did, and the friends he made there were not a replacement, but an addition to your social circle.
Now back home, Percy was getting back to being his old self quickly, and you were so glad your boyfriend was safe and sound.
Together again, you were in his cabin laying down next to one another as the moonlight lit the place. The son of Poseidon looked at you as if you hang the stars, his elbow propped up on the bed as he listened to you speak.