>I mean, Jesus,
>Corwin and Utena have to fuck to prevent Akio from driving a
>wedge between them? Akio? Christ, could this be any
>more of a betrayal to the characters, and the emotional arc that's
>been developing up until then?

No.

More detail? I would argue that Corwin and Utena fucking is both a consequence of their accepting that they can have the romantic relationship they've both wanted and a mechanism where Anthy can push that acceptance onto them. It's hard to lie to yourself that you are "everything but" when you are in the process of executing on the "but". And saying to a loved one that you want them to go out and have a good time and make love to another is a very strong statement, strong enough that Corwin and Utena have to pay attention.

Sex is emotionally a very strong action for most humans, and Corwin, Anthy and Utena are no exceptions.

This may have nothing to do with Gryph's perspective on it. But that's usually a sign of good writing if others can see depths that the author didn't consciously put there. This is because of baggage the reader brings with him...and I wonder what your baggage is.