@Knighto: My question is whether
Shin learned anything. Probably not.
What kills me is that the girls (now both of them, there's no excuse because the lighter-haired one (Aya?) explicitly referred to them as "going out" and the shorthair was in earshot) know that Shin and Yuki are a couple, but both of them--Yuki's "friends" are making openly salacious moves on her boyfriend; the light-haired one is worse, she's fine with anything happening as long as it means infidelity. Why is it that these FMCs keep such homewreckers as friends? You can't even call it backstabbing at this point, they're doing it in front of Yuki's eyes.
Worst thing is that Shin just sits there and lets it happen. Every. Single. Time. I wonder how much longer will he let this keep going, now that they're "lovers".
That said, I guess what you said is something I can agree with: did Yuki learn at all that her "friends" aren't friends?