A high-school student and the genius head of the Mikage Seminar, as well as the main antagonist of the second story arc of Revolutionary Girl Utena. Introduced in episode 14, Mikage too wishes to gain the power to revolutionize the world. However, rather than obtaining the Rose Bride, he wishes to kill her, and instate Mamiya Chida as the new Rose Bride.

He and Mamiya plan out their schemes in Nemuro Memorial Hall, the site upon which 100 students were buried alive. Throughout the course of the arc, he observes those amongst the supporting cast with psychological issues, and offers them a position in his seminar at Nemuro Hall. Bestowing Mamiya's black roses upon them, the students then act on their repressed desires as newly formed Black Rose Duelists.

He does not appear in the movie, nor in the original manga, although the movie does make visual references to his seminar. Later editions of the manga include a shortened version of the Black Rose Saga with an alternate ending.

SPOILER: Mikage was once a student known by the name of Professor Nemuro, in charge of a project at Ohtori Academy to 'revolutionize the world', which was seemingly the start of the Dueling Game. Unaware of the project's intentions, he spent his days 'acting as if he were a computer'. Upon meeting Tokiko Chida, he was greatly moved by her affection for her sickly younger brother, Mamiya. He then became committed to finding a way to extend Mamiya's life, despite Mamiya's lack of interest in doing so. At some point, Mamiya sets fire to the original Nemuro Hall, killing the original 100 Duelists.

By the end of episode 22, it is revealed that Tokiko has already grown into middle age and gotten married, while Mamiya died years ago. Despite this, Mikage has not aged. The next episode reveals that Akio Ohtori has been manipulating Mikage through his muddled, but strong memories, with Anthy posing as Mamiya. It is also revealed at this point that Mikage was the one who set the fire, presumably after seeing Tokiko romantically involved with Akio. After Mikage loses his duel to Utena, and Akio states that his usefulness has ended, Mikage 'graduates' from Ohtori. None of the cast members remember that he had been there at all, and no proof of him is left behind.

In the manga, his story maintains many plot beats, but is significantly shorter. After Mikage challenges her to a duel, Utena makes the discovery that Mamiya died long ago. This reveals to Mikage that he has been unable to let go of his regret at being unable to save the boys from the fire in Nemuro Hall, including Mamiya. After baiting her into attacking him, Utena fatally injures Mikage, and the building begins to collapse. As it collapses, Mamiya's ghost appears, and Mikage thanks Utena and Anthy for reuniting him with Mamiya. The two escape from the building and find his black rose ring on the ground.