For what it's worth, the whole immediate confession thing in the first episode was supposed to feel super sudden--it did in the manga, too, for both Yuu and the reader. You're supposed to wonder where Nanami's feelings are coming from, initially, just as Yuu does. The anime should explain it fully as it goes along. Same goes for the pacing switch-up--Yuu's life is supposed to feel, well, slow to start with.
Interesting. Yeah I picked up the series because people said the manga was good, I don't think I've ever read/watched a shoujo so maybe the pacing is a bit more foreign to me. I think what really helped this episode too is how the production flourishes totally worked, the kiss with the train going by and how that whole scene is directed, totally awesome.