Mouyuu assumes leadership of Nanban High School as the second leader, following her sister Moukaku. Known for her level-headed and honorable nature, she forms the rational counterpart within their leadership duo. Her story begins with a determined pursuit to assassinate Gentoku Ryuubi, sparking a confrontation with Shiryuu Chou-un. After their first clash, Mouyuu retreats upon realizing Chou-un matches her combat prowess. In a later battle, Chou-un decisively overpowers her, driving Mouyuu to attempt suicide rather than face defeat. Ryuubi's sudden power fluctuation interrupts this act, fundamentally reshaping Mouyuu's perspective on governing the Kanto region. This intervention causes her to abandon her assassination mission. She then forges an alliance with Seito to dismantle Kentei's stronghold within Nanban, preventing Kentei's full-scale revival. Mouyuu's arc concludes with her transition from antagonist to ally, driven by this pivotal event reshaping her philosophy of leadership and conflict resolution.