Peter knows that it’s coming.
It being his departure from Narnia, of course.
He’s told Aslan that he’s accepted the fact that he’ll never be able to return, but in truth, that acceptance is hard to reach. Unlike Susan, he doesn’t want to grow up. He wants to stay here. He can’t bear the thought of leaving. Walking away from his life like this, it hurts everything in him.
So when he stands upon the platform in front of both the Narnians and the Telmarines, it hits him like a ton of bricks. He can barely breathe as Aslan begins a speech— he’s unable to even listen to what he’s saying— and the realization that he’s leaving hits him harder than it ever has.
He can’t leave Narnia because it’s his home. He can’t leave Narnia because it’s who he is. But most importantly, he can’t leave Narnia because of Caspian.
If he leaves, he leaves Caspian.
He can’t bring himself to leave the prince that he’s ultimately fallen for over the past weeks that he’s been home. That would be the final blow to him. If he leaves, he can’t come back, and he can’t see Caspian again.
So when he feels Susan’s hand wrap around his bicep, his throat closes up, and he feels as if the entire world is closing in around him.
He can feel his legs moving, but he doesn’t actually know if he’s the one moving them.
And then it happens: a sudden burst of confidence runs through him, and he unravels himself from Susan’s grip.
He finds himself striding towards Caspian, who has the exact same look on his face as Peter. Caspian’s hands are suddenly clutching his cheeks and their lips are melded together, and Peter knows that he won’t be leaving. This is his forever home, and no one can tell him otherwise.
“I’m not leaving,” Peter murmurs, his forehead pressed against Caspian’s, “not now, not ever.”
“It would have been impossible for me to let you leave anyways.” Caspian whispers, before joining with Peter in another kiss.