He feels like he’s in the wake of almost, the space between everything he wants and everything he's never already gotten used to, with one part of him wanting to do nothing but leave and the other part of him wanting to do nothing but stay.
But it doesn't matter what he wants because he can't stay. Not when he still feels wrong, on the inside and the outside. And Sora is fine, and Kairi is going to be safe now, and the two of them are so obviously in love with each other that him staying here is just going to mess things up again. And he's happy for them because they really deserve to be together after everything that's happened, but there's part of him that just hurts because even if he didn't look like a monster right now, there's not going to be a place for him there, not in the way he aches to have one. He knows that he can't listen to the part of him that's trying to pretend it hasn't been stung and bruised, though, because he knows far too well what kinds of things will inevitably happen if he does.
He has to walk away, he has to remove himself from the situation before someone gets hurt. And he knows who Sora thinks he is, and he doesn't think anything could hurt more than that, until the point where he tries to walk away and Sora calls him by the name, confirming it out loud.
And thanks him.
That last part is just too much because that's just the way Sora is, and suddenly he has something caught in his throat. He needs to walk away, he needs to make a portal, he needs to ask Mickey for a way to keep him separated, anything to leave. And it's every single part of him now that wants to get away; the parts that're ashamed, that're guilty, that're trying to hold themselves together because he'll never be to them what he wants to be and he'll never tell them exactly what they are to him.
But then Kairi stops him, says his real name out loud, and he's not sure if Sora believes her. He tries to deny it, desperately hoping that he's the only one who can hear the infinitesimal waver in his voice. She convinces Sora enough to get him to walk closer, puts their hands together, and does... something that lets them all finally look at each other as they really, truly are.
And then Sora recognizes him.
"It's Riku, Riku's here..." And he doesn't think either of them will ever willingly let him leave now, and that might actually be okay.