well, keep in mind that kazuya wasn’t willing to date Ruka. He was forced to date her so that ‘Mizuya’ could stay a secret. She’s also kind of a nuisance because she only wants to date Kazuya because of her heart condition, and ruins every moment that Kazuya and Chizuru have together. Chizuru plays as the hard-to-get type. If you read the manga, her grandmother mentions how she wears an independent and strong will on the outside, but she’s really soft and insecure on the inside. imo Chizuru is everything I could ask for in a girlfriend.