When recollecting his experience of love after watching Hina's expressions(as she was glowingly absorbed staring at Takahashi), Rei recollects an experience, depicted by a girl climbed on top of him. The girl has a strong resemblance to his foster sister Kyouko. Is it ever confirmed, either in the manga or the anime, that this was an instance of sexual abuse? Or perhaps a past relationship that Rei had? Given Kyouko's rather unstable behaviour, it wouldn't be very surprising but I'd like to know what exactly was that recollection about.