Who's the character in the middle of this WIXOSS cast picture?
Her name is Honoka. She's a part of Kazuki's circle of friends. In episode 6 of the first season she and a couple of other girls confront Yuzuki about her relationship with her brother. In episode 8 she leads Kazuki out from the card shop where they're playing together in order to confesses her feelings to him. When she's rejected, she tells him what people have been saying behind his back.