Poor gyaru. We know she exists to lose, but she's already a better character. Amano pulls the "kyaa ecchi*slap*" constantly and won't just tell him she likes him, and early smart girl isn't even in the story so I don't even remember her name.
Here's kind of the strangest part to me. This made sense when she was just a bored sadist who liked him the way a cat likes a mouse. Having her actually want him just makes her look like an idiot.
Can...can we just go ahead and get whatever stupid explanation the author is going to give for this and move on? I don't even care what it is at this point. Tell me the hero uses photosynthesis to live, and it'll probably still make more sense than wherever this is going.
I'm with @Siikalahna on this. It was totally his fault. There was no reason not to have her with him in the line. It happened solely to allow the next plot point.