Kosuri was raised in a privileged household, with her father, Keisuke Onigashira, being a wealthy arms dealer who initially supported Japan’s strict censorship laws for personal gain. However, as the government’s regulations tightened, even Keisuke began to question the extreme levels of censorship, leading to his eventual support for anti-censorship efforts. Wanting to give his daughter a chance to be part of something greater, Keisuke introduced Kosuri to SOX, believing that fighting against censorship would teach her the value of true rebellion.

Unlike Ayame Kajou, who fights for freedom of expression, Kosuri sees rebellion as a means of gaining attention and excitement. She idolizes violent and radical revolutions, mistakenly believing that SOX should function as a terrorist group rather than an ideological movement. When she realizes that SOX’s tactics are more strategic than chaotic, she becomes frustrated and impatient, ultimately leading to conflict within the group.

Kosuri is short and petite, often being mistaken for a child due to her small stature and youthful features. She has light purple hair styled into puffy twin buns, which resemble the shape of an onigiri (rice ball) a play on her last name, Onigashira. Her large, expressive eyes and seemingly innocent smile give her the appearance of an obedient and harmless girl, which contrasts sharply with her manipulative and rebellious tendencies.

She wears the standard Tokioka Academy uniform, but when participating in SOX activities, she dons a modified version of Blue Snow’s disguise, featuring a smaller cape and mask. Despite her cute and childlike looks, her expressions shift dramatically when she reveals her cunning or frustrated side, showing her true, more aggressive nature.

Kosuri Onigashira is cunning, manipulative, and impatient, often presenting a false persona to get what she wants. At first glance, she appears sweet, obedient, and eager to support SOX, but beneath her innocent facade, she is calculating and self-serving, only remaining loyal as long as it benefits her. Unlike Ayame Kajou, who fights for freedom of expression, Kosuri sees rebellion as a form of personal excitement, craving chaos and destruction rather than meaningful change. This misunderstanding of what it means to be a revolutionary leads to tensions within SOX, as she often pushes for more extreme tactics that could jeopardize the group’s mission.

Her biggest flaw is her impatience, as she expects immediate results and becomes frustrated when things don’t go her way. When she feels underappreciated or ignored, she lashes out, throws tantrums, or betrays those around her to gain attention. She frequently manipulates others by acting cute and innocent, but the moment she is denied what she wants, she shows her true selfish and aggressive nature. Despite her troublesome personality, Kosuri is not inherently malicious—she is simply young and naive, struggling to understand the difference between reckless anarchy and meaningful rebellion. Over time, she begins to grasp the importance of strategy, but her self-centered tendencies never fully disappear, making her an unpredictable and unstable ally in SOX’s fight against censorship.

• Joining SOX & Early Excitement
  Kosuri joins SOX with high expectations, believing that the organization is a radical force of destruction. Initially, she admires Ayame and Tanukichi, eager to prove herself as a valuable member of the team. She assists in various SOX missions, though her methods are often excessive or inappropriate, causing friction with the rest of the group.

• Disillusionment & Conflict with SOX
  As Kosuri realizes that SOX’s tactics are more calculated than chaotic, she becomes restless and frustrated. She questions Ayame’s leadership, believing that SOX is not extreme enough, and begins to act on her own, causing problems for the group. Her recklessness and impatience lead her to make impulsive decisions, including betraying SOX in a moment of frustration.

• Redemption & Growth
  Despite her betrayal, Kosuri eventually realizes her mistakes and returns to SOX, though her self-serving nature remains a core part of her personality. While she still craves excitement, she begins to understand the value of strategic rebellion, making her a more controlled but still unpredictable member of the team.