I get the feeling that Harumachi applies the word "rape" very loosely. The impression I'm getting is basically "to force someone to have sex with you on your own terms rather than theirs", which aptly describes the final match: Shino doesn't mind having sex with Yoshino, but she wants to do it at her own pace (both to win and as a survival tactic; if she loses she stands a high chance of becoming addicted to her opponent's methods of stimulation), while Yoshino's fetish is all about forcing others out of their comfort zone and into her merciless rhythm, ultimately overwhelming them to the point of addicting them to herself, with her sister Shino as the object of her greatest desire.