He thought he was over it.
He and Adam were becoming closer every day. Adam was trying hard to fill the empty space in Kurt's heart in the shape of everything he and Blaine had shared, to fill Kurt's mind with new, romantic memories in place of the history that still made his heart ache every now and then, when a familiar song would play or a secret joke would be called to his memory.
It still hurt sometimes, but… Kurt thought he was moving on.
Until graduation day.
He held Adam's hand and laughed with Rachel, although he didn't have a clue what she'd just said. His gaze kept creeping over to a spot across the room, where Blaine stood wearing a bright red graduation robe, hair tousled by the mortarboard he held in his hand, and a bright, beaming smile on his face. As Kurt watched, the tall blond beside him cast an easy, casually protective arm around Blaine's shoulders, and that quiet elation, the beautiful softness in Blaine's eyes as he looked up at Sam, nearly stole Kurt's breath.
Kurt remembered when Blaine used to look at him that way.
But he hadn't – not in a very long time. Not since long before the cheating – and Kurt didn't have to wonder why.
Sam looked at Blaine as if he was his entire world, affection in his smile as he laughed at something Blaine had just said, then leaned down to press a brief, soft kiss against Blaine's lips. The way Blaine seemed to freeze in surprise, and then just melt into the kiss, drinking in the sort of blatant affection that Kurt had always been too afraid to show in these halls – Kurt knew that he hadn't been giving Blaine what he needed, not for months before their breakup.
It was no excuse for cheating, but now, in hindsight, Kurt could imagine what it must have felt like to be in Blaine's position in those lonely weeks right after Kurt left for New York – alone in a strange place, without the support of the person he'd come there for in the first place, with little reassurance that their relationship even mattered to Kurt at all anymore.
Judging by the warmth in Sam's eyes, the subtly intimate slide of his hand down to rest at the small of Blaine's back as they headed slowly toward the exit – Sam wasn't leaving any question at all as to how much Blaine meant to him.
Kurt had planned to say hello before he left to go back to New York, but as he watched Blaine go with a bittersweet smile, he decided to simply leave it alone… and let him go.