While I do like Yuu x Touko, I'm not fully convinced when it comes to this pairing. I think it's adorable that Yuu is slowly starting to notice how she views Touko, but it kills me to see her have to keep her feelings locked away. Yuu is trapped in an all-give-no-take relationship where she is forced to tread carefully or risk destroying their friendship (?) entirely. Meanwhile, Touko is able to do whatever she wants freely with no strings attached. She can display her affection towards Yuu and announce her feelings towards her without worrying how it changes their dynamic.
Although I understand it was entirely Yuu's choice to let Touko do whatever she wants and to have entered this kind of unique relationship in the first place, it's really hard to blame her for what she's feeling now. All I can say right now is that Yuu is just stuck between a rock and a hard place.
But the real reason why I don't fully support Yuu x Touko (yet!) is because we don't know nearly enough about Touko. Obviously, since we've been viewing all of these events through Yuu's eyes, we know that her stance on love has gradually changed. Meanwhile, Touko's has remained the same for the most part. She's just having her fun exploring the thrill of being around the one she likes and doing whatever she wants without consequences. I can't blame Touko either because she is under the impression that Yuu is okay with anything. Basically, because I don't know whether or not Touko will change, part of me fears that Touko will never start to think differently about Yuu.
I like Yuu x Sayaka better for weird reasons though. For one, I like the idea that they don't idolize each other like how they both view Touko. I see some room for development for these two, but that would only work if Touko is unable to change the way she thinks of relationships and Yuu. Right now, Touko seems to be very focused on self-development instead of trying to understand the people around her. That kind of selfishness bothers me, even if both Yuu and Sayaka allow it.
I don't know, I'm kind of rambling now, haha.