Yuzuki's twin brother. He introduced Yuzuki to the game, and was the one to give her the deck containing Hanayo. Kazuki is one of the few non-Selectors to know about WIXOSS' secret.
He seems to be unaware of Yuzuki's feelings.
When Hanayo replaces Yuzuki, she confesses to him that she had always loved him, then he tells her that he has the same feelings and they start dating.