The part of his life he [can't] always remember.
He wasn't going to remember her.
He just- knew- in his heart. Like this had happened before, but in a different manner.
Already he was forgetting the little things, like the almost-there pinprick scars around her lips that vanished if you looked too closely and her laugh and the look in her eyes when she cried. Gone, though he had no way of knowing.
Just the faint inkling that something was wrong.
It was only a matter of time until the rest was gone. Maybe no more than minutes. It was cruel to her, because she didn't deserve to be forgotten, and cruel to him, because he'd come this far without forgetting anyone- except it felt like he had but he hadn't, couldn't have- and it wasn't fair that the first person he had to forget was her-
Had he ever known her name, or was that gone, too?
There was the fleeting impression of a girl who talked with cards, the crinkling of ice cream wrappers, a scolding for not sleeping.
He'd danced with them. That felt important, but already the memory was gone. Something about sweets-
He remembered a seasalt kiss.
Then that too was gone, and Riku was left standing with the evening sun lighting up tears on his face that he couldn't recall crying.