@Giga: After re-reading what I post and your points along, now I kind of agree with you. My third point kind of contradicts my own argument (he even tells her to stop, so she didn't have his permission at first).
I agree that both cases were rape, but I still consider that in the first one there were not such perverse motives as in this one (I do not justify rape, whatever its motive is still a criminal and horrible act); the other time it was with good intentions: to satisfy him (although she went way too far, and 'cause of that she felt guilty) and this time it was because she believed Hikaru deserved a lesson, that is, it was a deserved punishment.
Tho', I also consider that this behavior of Chintauro was strange and out of character, but it could be justified that the spark that detonated both rapes was different, and because of that this time she did not feel guilty.