He'd probably be devastated. Percy loves Annabeth deeply, so this would be like a punch in the gut for him.
At first, Percy might be in denial. He'd think it was some kind of joke or a mistake. But once he realizes it's real, he could become angry. He might confront Luke and Annabeth, demanding an explanation. And then he could go into a state of depression, feeling like he's lost a part of himself. In the long run, he might try to become a better person or hero to prove to Annabeth that she made a mistake in leaving him.
Percy could be very confused. He might not understand how Annabeth could suddenly choose Luke over him. He'd start to question their entire relationship, thinking about all the things they've been through together. He may also feel betrayed, not just by Annabeth but also by Luke, since Luke was supposed to be a friend at some point. His reaction would likely be a mix of emotions that would drive his actions in the fanfiction for a long time.
Annabeth would likely be furious at first. She has been through so much with Percy, and for him to leave her for Calypso would seem like a betrayal. But then, she might also start to reflect on their relationship and what went wrong. She could become determined to win Percy back or to move on and prove that she doesn't need him.
Annabeth would probably be very hurt at first. She has a strong bond with Percy, and his leaving for someone else would be a huge blow to her self - esteem and her heart.
Percy could be heartbroken. He might initially go into a state of denial, not believing that Annabeth would actually leave him for a mortal. He might keep thinking there was some mistake or that she was being influenced in some way.
He could go on a desperate search for her. Percy is a very determined person. He would try to find out the reason for her leaving. He might ask all their mutual friends and look for clues everywhere. Meanwhile, he would also be trying his best to take care of their child. He would be heartbroken but also focused on keeping their family together in some way.
Well, one reason could be that in the fanfiction, the writer might want to explore a different dynamic. Maybe Annabeth gets lured by Luke's charm that has been newly developed in the fanfic. Luke could be presented as more understanding or having a different kind of allure that attracts Annabeth away from Percy.
Percy would probably feel a mix of shock and confusion at first. He might wonder why Annabeth left him with this huge responsibility. Then he would start to feel a bit scared because he doesn't know if he can take care of the child properly.
Well, Percy is a complex character. His reaction could depend on how much he knew about the pregnancy before Annabeth left. If it was a complete surprise, he might be in denial for a while. He could also start to blame himself, thinking he had somehow failed her. And then he might eventually turn that pain into a determination to be a better person, whether or not he ever sees Annabeth again.
In the long run, Percy might grow from the experience. He could become more cautious in his relationships and less trusting. Or, if there's a chance for redemption in the fanfic, he might be open to forgiving Annabeth if she shows true remorse and has a valid reason for her actions. But initially, it would be a very difficult and emotional time for him.
Well, Percy could have a range of reactions. At first, he might be in denial, not believing that Annabeth would actually leave him for a job. Then, as it sinks in, he could get angry. He's a passionate guy, and this would be a big blow to him. He might also feel a bit of envy towards the job that seems to have taken Annabeth away from him. In the long run, though, he could use this as a chance to grow on his own and become more independent.
Percy could also be the type to demand an explanation from Annabeth. He wouldn't just let it go without trying to understand why she did it. He's not a pushover, and his relationship with Annabeth was important to him, so he would want to know what led to this betrayal.