As I said in the spanish chap, aherm:
So what's next? They gonna reveal that Yami also took Hikari's virginity too?
If so, it was TOTALLY foreshadowed guys, like for real. Back when Yami almost frenched Hikari, it was cause they had always been a couple behind the scenes, but we just didn't see it is all.
And Hikari's attraction for Yuu was cause she sensed Yami's essence still lingering in him.
So when she saw them face fucking, her shock was cause she saw her GF cheating on her.
Trust me, I'm a physician.