That was a nipple, wasn't it? Disrupting the smooth flow of the Prince's body, but not entirely unwelcome. It was slightly peaked from the cooler air like it never was when Riku bathed the Prince.
Dimmly, Riku was aware of a sharp tugging, but he couldn't concentrate on it, leaning his head back instead as the Prince trailed hot kisses down his neck to his collar, nosing there at the material and yanked again on his shirt so that Riku finally laughed breathless took his hands off the Prince long enough to help him strip his shirt off, giving his head a little shake once it pulled free to send his hair cascading over his bare shoulders.