Mouyuu holds the position of second leader at Nanban High School, succeeding her sister Moukaku. She is portrayed as the more level-headed and honorable of the two siblings. Her initial story focuses on a determined campaign to eliminate Gentoku Ryuubi, bringing her into conflict with Shiryuu Chou-un. In their first encounter, Chou-un, despite being nude, matches Mouyuu's combat strength and forces her retreat. Mouyuu later challenges Chou-un to a rematch but suffers a decisive defeat. Facing this loss, Mouyuu attempts suicide. This act is interrupted by a fluctuation in Ryuubi's power, an intervention prompting Mouyuu to reevaluate her ambitions for ruling Kanto. This event triggers a major shift in her allegiance. Mouyuu abandons her previous goals and joins forces with Seito. She actively participates in the assault on Kentei's lair within Nanban High School, proving instrumental in halting Kentei's full revival.