Sora was sure that he'd see Corin later, he had a lot of people to see tonight. And really...he did not even mind if Riku wanted to split up. The fact that he knew he'd have the other man in his bed tonight was so...reassuring (and exciting) that he wasn't even that bothered about it. (Emotional growth Sora, very good.)
The Prince watched Riku for a while. He had no doubt that Riku was handling whoever it was beautifully, but he didn't know everything. Sora wanted to be there to bail him out if he needed it. "Thank you, Corin. I will see you later!"
He headed up the stairs, acknowledging a few people with a nod, and came back to Riku's side with a hand on his shoulder to let him know he was there. "I apologize for the interruption." He wasn't interrupting, he was the Prince, he could do whatever he wanted. But he was a polite Prince.