...and the devils advocate says:.........*spoiler's; be warned
While the rest of you rejoice another reason to dis Yamato for wat he didn't do, I hope there are at least someone out there trying to understand why exactly Yamato did what he did.
True: he is a jerk for not answering straight away or comfort her to at least dispel some of uncomfortable atmosphere. But given his selfish nature at least he decided not to overlook Yui's eye shutting and facing away at that very crucial moment right before he 'crosses the line'. For a guy that doesn't immediately focus on sex everytime he is approached by a naked girl (unlike some people......) I don't know why he should respond as you would for Yamato to avoid using 'victim's sympathy' to score his first. Very idealistic in the romantic department but sadly disapointing to the fans who.....well, we know what they'd expect ;). Its not like he doesn't want to (hence the throwing Yui into missionary position) but looking into Yui's (closed) eyes pretty much turned him off. You think too much Yamato, get your act together.
Ah well, good luck Miki and Honoka, and maybe even Yui for a second chance. I'm still hoping for a near death experience to happen to wipe out Yamato's memory of Suzuka so that he can get his messed up life together. Hopefully it'll give him a clean slate to work with so that the fans might eventually forgive Yamato.
EDIT: to those confused by the 2nd paragraph, I mean to say that while Yamato gets points by considering Yui's hesitaion and being a man by not playing out the victim role for sex, he immediately loses it for his selfish behaviour afterwards.