Does Yui even like him? I get the feeling she only likes being in control, which is why she got so anxious when Kei was getting all chummy with Yo and why she never looks like she's enjoying herself when Yo is proactive.
LOL Idk what she expected, just randomly brought him over, told him to strip, and was like: "fuck me"?
That would kill most people's boners even if he wasn't screwed up by Kei