Her fingers only twitched when he showed up.
Riku watches her from his seat near the window. Kairi's on the floor, with blank, drooping eyes and legs sprawled out in unnatural positions. The girl was born with glue for a spine. He can press his foot on her back, and she'll bend forward like no other human can.
The ship rocks again, and Kairi falls to the floor. Riku immediately gets up, and goes to her. He may be dirty and dark and tainted, but he's not heartless. With one hand on her back and the other under her neck, he pulls her up to sit again. He under-estimates his strength, though, and unwittingly pulls Kairi into his lap.
Her head lolls in her mock slumber, and her hair tickles his cheek. Riku freezes up, because Kairi's movements remind him of Maleficent and he doesn't like Maleficent. But Kairi is Kairi and Kairi is just sleeping, she's just sleeping. She's not--
Riku's breathing stops and he can hear his heart as Antisora presses a cold kiss against the back of his neck. He still wishes that Antisora was just Sora. He wishes that Sora didn't leave him behind with a corpse and a shadow.
But Sora was bound to get bored of an obsessive best friend. Riku had known it was only a matter of time before Sora left him alone.
But Antisora is the side of Sora that Sora never was. Antisora will never get bored of his Riku. But, that's only because Antisora is a machine, programmed to be Riku's friend, Riku's fucktoy, to be Riku's everything. Riku still pretends that Antisora's skin is tanned and not black like his soul.
At this point, Antisora's pushed Kairi onto the floor, where she lays like a broken doll. Antisora pushes Riku down as well, onto his back, and the Heartless straddles his master. Antisora takes Kairi by the hair, and lays the girl's head on Riku's chest.
Riku isn't sure what's heavier. The deadweight of Kairi. Antisora.
Or the guilt crushing his spine because he left the light.