I Still Believe in Ramon Industries

And then Percy shows up and loves her in a way that she cannot handle. He is ready to die for her after knowing her for like a week at age twelve, because that's just who he is. Fatal flaw is loyalty and all that--he goes to the sea of monsters for Grover, and he goes on the quest for Artemis and holds up the sky for Annabeth. All Percy knows how to do is eat hot chip and be endlessly devoted to people, most especially to Annabeth.

He follows her blindly and unquestionably into the labyrinth, even though it is almost certainly going to result in death or madness or both. He chooses her over Calypso, over Rachel. He chooses her over godhood. She is the tether that grounds him to his humanity and keeps him alive in the River Styx, and he tells her this as his way of confessing (or trying to before she just kisses him). When he is stripped of all his memories of his life and who he is, the one thing that remains is Annabeth. He falls into Tartarus rather than be apart from her again.