Miki Kaoru is a thirteen-year-old seventh grader at Ohtori Academy and the youngest member of the Student Council. He is known for his androgynous beauty, gentle demeanor, and exceptional talents. He is a prodigy pianist, a skilled fencer who fences at a national level and is nearly as accomplished as Juri Arisugawa, and an academic genius who takes college-level courses despite his age. Miki often carries a stopwatch, which he clicks to time mysterious intervals, a quirk that adds to his distinctive presence.

Miki’s background is defined by his relationship with his twin sister, Kozue Kaoru. As children, the two shared a deep bond through playing piano duets, and together they composed a piece titled The Sunlit Garden. However, a failed concert—during which Miki fell ill and Kozue was forced to perform alone—revealed that Kozue lacked true talent and had been carried by her brother’s skill. Embarrassed, Kozue stopped playing the piano entirely, and the rift between them deepened. In the present, Kozue is sexually promiscuous, often dating boys to provoke Miki’s jealousy, while Miki resents her choices and feels a profound sense of loss for the pure connection they once shared. This loss drives his search for “something that shines”—an ideal of purity and talent that he believes he has lost.

Miki is polite, ingenuous, and initially idealistic. He is the only Student Council member who openly befriends the protagonist Utena Tenjou, helping her and Anthy Himemiya with homework and treating them with respect. Despite this, his idealism is also a weakness: he projects his longing for his sister onto Anthy after hearing her play The Sunlit Garden, developing a crush on her and believing she embodies the shining thing he seeks. Manipulated by Touga Kiryuu, Miki challenges Utena to a duel, claiming he wants to protect Anthy’s piano playing from being controlled by Utena. In reality, he desires to possess Anthy as a replacement for Kozue. During the duel, Anthy cheers for Utena to win, shocking Miki and causing him to lose; this moment forces him to realize that Anthy has her own will and does not need his protection.

After his defeat, Miki largely returns to a friendly role, though he remains entangled in the dueling system. He is targeted during the Black Rose Saga, as a sword is extracted from his chest by the Black Rose Duelist. In the Apocalypse Saga, he is convinced by Touga to visit “the end of the world” and subsequently challenges Utena to a rematch, this time with Kozue serving as his Rose Bride. During the duel, he becomes distracted when Kozue attempts to seduce Anthy, leading to his second loss. This confrontation helps Miki begin to disentangle himself from his possessive fixation on his sister. By the series’ end, he appears freer from Kozue’s influence and more able to grow into his own person.

In the film The Adolescence of Utena, Miki’s relationship with Juri is emphasized, and his resentment toward Kozue becomes more overt. A scene shows them bathing together, where he tells her they can never be as close as they once were, and Kozue threatens him with a razor. His role in the film is more peripheral, but his arc mirrors his desire to break free from his sister’s hold.

His notable abilities include masterful piano performance, fencing with an épée, and extraordinary academic aptitude. He is also observant and methodical, as reflected in his stopwatch habit. While he often acts as the moral conscience of the Student Council, his vulnerability lies in his inability to accept change and his tendency to idealize others—a flaw he must overcome to move toward genuine maturity.