He's pulling drawers, testing the existence of empty space, and that's when he finds the photograph, face down, like someone took a shortcut cleaning up and forgot to put it back after. He turns it over and pauses. There's him, and there's Naoto, and—
He should know these people, is the thing, but he doesn't. Those grinning faces, that triumphant air—it's like a shot from one of those crappy growing-up flicks. Freeze frame, and the narrator says that he never forgot those shining teenage years he spent playing with his friends.
Nobody in those movies ever got amnesia.