Touya would have to be pretty weak-willed if he believes that his chances are 0 with Rina just because the musicians consider him to be a tool. Considering it's Touya we're talking about though, that's actual possible
. I still believed he should've made up a white lie. It's not like he's been the most honest character throughout the series...
I don't think Rina would tell Yuki about this though, since she's protective of her kouhai and wouldn't want to hurt her. Also, Rina mentioned in the episode that Yayoi is Yuki's support and that she's essential to the fledgling singer. Telling Yuki that her boyfriend is having an affair with her "essential support" would be beyond devastating.
Although I feel like Yuki is still going to find out about the affair, it won't be through Rina. I can already imagine Yuki discovering everything by seeing Yayoi and Touya making out in the car. Her facial expression would probably be even better than Rina's
