They swore they’d be together forever - they’d take on the world ( universe ) together. But Person A is the chosen one. They’re the one prophesied to save the world. Person B isn’t. And while they were together as children, Person A left when they were barely a teenager to start training. And B? They started training too. Each grew, on two different paths.
B became a leader of their oppressed community, protecting their people and navigating them through the world and its harsh conditions alone.
A grew and trained and after years apart from B, they return, and fulfill their destiny, swooping in to destroy the great evil and save their friends.
They expect B to be happy. They did it. And B is. At least, about the thing being gone. Because after it? After the battle when A goes to talk to them? B doesn’t acknowledge their existence. B pretends A is nothing more than a stranger. And it hurts. Somehow more than any of the obstacles A faced before.