Rui was always the one who initiated things when Shion was a guy, so I don’t think that’s the problem. In this case he just got interrupted by Shion turning back. Both Ryu and Shion were playboys up until now, so Rui is most likely having a similar dilemma.
It’s like the writer tries their best to find some type of way to makes things even more insane, and I’m so weirded out to the point I can’t stop reading it ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄
What a cute chapter (≧∀≦)