Kozue Kaoru

Kozue Kaoru is the twin sister of Miki Kaoru, a duelist and a student council member. With her brother in the student council and already in high school though he is of middle school age, it's clear Kozue lives in Miki's shadow, a fate she quite dislikes. However she still deeply cares for and loves Miki, and reveals in the Black Rose saga that she purposefully dates men she knows he will disapprove of because she enjoys having him worry about her. It is Miki's growing infatuation with Anthy Himemiya that makes her become a Black Rose duelist, as she says she can feel him "slowly fading away" towards Anthy. She is extremely protective of Miki, going as far as to push a music teacher she feels is a threat to him down the stairs.