soft shoulder
Renji had never considered Rukia as girl. She had always just been there, talking like a boy, fighting like a boy – hell, even snoring like a boy.
So one time, when he was carrying her on his back (she had broken her ankle, the idiot brat), he was actually surprised when he felt something …womanly against him. Another time he accidentally crashed on her when she was bathing in one of those dirty rivers and convinced himself – yep, definitely a woman.
Now that they were older, Renji saw Rukia as raw strength, inner strenght and he thought that even though she was so skinny that her wrists could be snapped by his two fingers, it would be his head to fall if they fought head-on.
Rukia had never considered Renji as a man – or maybe a man, but then again, all men were beasts.
Sometimes he acted like such a wuss that she just wondered if he was a girl (not that being a girl makes you a wuss, but hey, the idea) so as a payback for the incident in the river, she catched him off-guard when he was bathing but of course she already knew what she'd see.
When they got older, Rukia saw Renji as hairmusclesleanbody and she actually noticed that he was good in whatever it was he was doing: being a man – a beast – and annoying the hell out of her.
Now that they were lying there it didn't matter which one of them was the woman and which one the man – it was enough to just be there.