Oh my lord, Ruka is so self-absorbed. She just cares about herself. Her attraction to Kazuya is about how he makes *her* feel. She knows he wants someone else and she's just trying to force him into loving her. She's manipulative and the narrative presents her as some sort of poor soul who doesn't receive love. LOL fuck her
Also Kazuya doesn't even think about setting boundaries if that means having that bit of contact with a girl's skin. Wait no, for him it's sufficient to just breathe the same air. Goddamnit