To make this short, I'll bullet point this situation..
1. A man and woman are in bed, kissing and such.
2. The girl made it VERY clear she did not want to have sex with the man
3. She however, agreed to him rubbing his penis on her vagina
4. They do that, but at some point, it slips inside and the man does not stop having sex...
5. The woman is unaware that it slipped inside but is informed by the man, after he ejaculates, that he did penetrate her.
IS THIS RAPE? What are your thoughts?