@Idle as always Ruka is a toxic, unhealthy person. She found herself with an immature young adult who is also a virgin... the only thing maintaining this closeness between Kazuya and Ruka is her harassment and his sexual immaturity (which I find despicable). Therefore, I don't think Ruka is a victim, since she clearly understands that Kazuya is "in love" with someone else. Ruka is a toxic person obsessed with someone who doesn't reciprocate her romantic feelings.