Kozue Kaoru

Kozue Kaoru closely resembles her twin brother, Miki, but has more outward-flipping blue hair, closer to purple, and striking blue eyes. Her hair is noticeably wilder than Miki's. During the Akio Ootori arc, when taking the role of the "bride," she wears a blue dress.

Kozue exudes a mature and somewhat sullen aura, with hints of rebelliousness. She is emotionally complex, holding an intense, warped love for Miki that is reflected in her unpredictable actions. Despite her popular image among male classmates, she often uses romantic relationships to provoke her brother rather than out of genuine affection.

Kozue was once praised for her childhood piano playing alongside Miki, a memory cherished by her brother. However, her own talent was lacking—Miki was the true prodigy, often covering for her during duets. This contributed to her complex relationship with him. She endures familial issues, discarding letters from her parents and stating outright that she does not need them. Even when injured, she downplays it, likening herself to a wild animal with a quick healing process.

During the Black Rose arc, Kozue's duel weapon is a black sword that she draws from Miki’s body.

Kozue’s relationship with her twin brother, Miki Kaoru, is central to her character. She possesses a deeply conflicted emotion toward him, oscillating between jealousy, desire for his attention, and possessiveness. She attracts much attention from boys, and bluntly claims to her friends, "I didn’t replace a boyfriend, I just added another one." Kozue’s possessiveness extends to violently warding off people she feels threaten her bond with Miki, such as pushing his piano teacher down the stairs.

Childhood and Musical Past

As children, Kozue and Miki played piano side by side, earning admiration for their duets. However, Kozue's actual ability was lacking, relying on Miki to support her musically. This once-special memory became a source of tension as she struggled with her own shortcomings.

Strained Sibling Relationship

Despite Miki treasuring their childhood, their current relationship is strained and distant. Kozue’s warped love manifests in destructive behaviors—she goes out of her way to hurt herself emotionally, engaging in reckless romances with boys Miki dislikes, just to get a reaction from him. At the same time, she fiercely defends her brother from outsiders, going so far as to harm his piano teacher out of jealousy.

The Duel and Black Rose Arc

During the Black Rose Society arc, Kozue enters a duel representing "obsession" (attache). Her weapon, a black sword, is dramatically extracted from Miki himself. On the dueling table, a milkshake sits, but Anthy Himemiya—another main character—drinks some of it during the match.

Akio Ootori Arc

In the Akio Ootori arc, Kozue motivates Miki to duel again after he becomes disillusioned by manipulations from adults and family matters, including a letter from the End of the World and their parents' remarriage. She tells him, "If everything around you is dirty, you have to get dirty yourself to get what you want," pushing him into a second duel for Anthy’s possession.

Manga and Movie Adaptations

In the manga, Kozue’s role combines aspects of Nanami Kiryuu’s character, and her obsession with Miki is portrayed even more directly. In the movie, she aggressively tries to keep Miki from leaving her, even resorting to a knife. Later, her name appears on the license plate of a black car, though it is uncertain whether Kozue herself has transformed into the vehicle.

• Popular among boys, Kozue is frequently gossiped about for her numerous boyfriends.
• She claims not to replace boyfriends but to "add" them.
• She is marked by the Dueling Society as "Obsession" (attache).
• Shows extreme independence, even rejecting her own family.
• In the manga, her obsession with Miki is more intense and straightforward than in the anime.

"Everyone else should just disappear. Except for me and Miki—everything else is ugly!"

• Age: 13
• Birthday: May 28
• Zodiac Sign: Gemini
• Blood Type: O