Rin Onigawara’s childhood was marked by family turmoil. Her parents divorced after her father’s affair and subsequent departure, leaving her mother emotionally devastated. Unable to cope, her mother projected her resentment onto Rin, blaming her for the family’s collapse. Because Rin bore a strong resemblance to her father, her mother repeatedly insulted her appearance, calling her “ugly” and the “child of a monster.”

In response to this emotional abuse, Rin began wearing a demon mask, believing it would shield her from her mother’s scorn and atone for what she perceived as her own “sin.” Over time, the mask became a central part of her identity, to the point that Rin now habitually wears it in public as both a shield and a symbol of strength.

Rin Onigawara is depicted as a slender, fair-skinned young girl with short black hair styled in a traditional bob cut and striking purple eyes. She is most often recognized by the demon mask she habitually wears, a symbol that has become inseparable from her public identity.

Her standard attire is the Aichi Symbiosis Academy uniform, complemented by her katana, which she consistently carries at her left waist. On rare occasions, such as during special events with Fudou Nomura, she is shown in alternate attire similar to the other schoolgirls. Despite the intimidating aura of her mask, Rin is considered a beautiful young woman, and her appearance reflects both her discipline and her hidden vulnerability.

Rin Onigawara is initially portrayed as hostile toward men, earning a reputation for her uncompromising attitude and strict enforcement of the academy’s rules. Her severity and mercilessness in battle often forced transfer students to withdraw, resulting in her class consistently having fewer students than others.

Over time, however, Rin’s interactions with Fudou Nomura reveal a more complex side to her character. After he openly defies her authority and defeats her in combat, an encounter punctuated by their accidental kiss Rin begins to develop feelings for him. Their relationship allows her to gradually lower her defenses, showing vulnerability and emotional honesty. She eventually confides in Nomura about the origins of her mask, rooted in her mother’s scorn after her father’s infidelity and departure.

Nomura’s reassurance, particularly when he tells her that her face is “pretty,” has a profound effect on Rin. His acceptance inspires her to momentarily set aside her mask and gain the confidence to face others without it. In turn, Nomura’s willingness to return the mask and share his own painful past deepens their mutual trust, highlighting Rin’s growth from a cold enforcer into someone capable of warmth and emotional connection.

Master Swordswoman
Rin is a highly skilled practitioner of the Kashima Shinden Jikishinkage-ryū style of swordsmanship. She demonstrates remarkable precision, dexterity, and control with her katana, capable of striking with such force that the mere pressure of her blade once cut Nomura’s cheek. Her mastery has allowed her to defeat formidable opponents, including Warabi Hanasaka, an accomplished swordswoman of the Taisha-ryū style.

Sword Techniques

Horizontal Strike (横一文字, Yokoichi-Moji): A swift and powerful horizontal slash.

Dragon’s Tail (龍尾, Ryūbi): A circular slash delivered with sweeping momentum.

Blur/Haze (霧, Kasumi): A precise and forceful thrust attack.

Chest Strike / Chest Taker: A charging thrust in which Rin holds the blade with one hand while driving it toward her opponent.

Crane Stance (鶴の構え, Tsuru no Kamae): A one-legged stance inspired by the posture of a crane, used to counter low attacks and maintain balance.

Carpenter’s Square (曲尺, Kanejaku): A concealed downward slash technique that is difficult to evade, as Rin can alter the range by adjusting her grip.

Cycle: A hidden technique in which Rin uses controlled breathing to unleash a rapid series of slashes within moments.

Enhanced Physical Abilities

Strength: Rin’s strikes are powerful enough to crush or fracture bones, a trait noted by Warabi Hanasaka.

Speed: Her reflexes and agility allow her to match Nomura’s movements briefly and contend with Hanasaka’s high-speed assaults.

Endurance: Rin has demonstrated resilience in battle, continuing to fight even after sustaining severe injuries, such as deep cuts to her shoulder and back.

Breathing Techniques

Reverse Breathing / Mirrored Breathing: A specialized Kashima Shinden technique that enhances her physical performance. By coordinating her breath with her movements, Rin can temporarily heighten her strength and speed, enabling explosive bursts of combat ability.

Fudou Nomura
Rin’s first impression of Nomura was negative, viewing him as a delinquent in need of “correction” like the other male students at the academy. Their initial confrontation ended with her defeat and an accidental kiss, leaving her humiliated. Despite this rocky beginning, her feelings toward him began to change, particularly after he made remarks that left her flustered, such as expressing a desire to see her in ordinary clothes. Over time, she developed romantic feelings for him, though she often reacts with jealousy whenever he interacts with other girls.

Their relationship deepened after the incident in which Satori Tamaba framed Nomura, leading Rin to torture him in anger. Upon learning the truth, she felt remorse and allowed him to remove her mask as a form of “punishment.” Rin later confided in him about her troubled childhood, revealing the reason she wore the mask. In turn, Nomura encouraged her to wear it if it gave her comfort and shared his own past of loss and abuse, marking a moment of mutual trust and emotional intimacy. By the end of the second semester, Rin resolved to follow Nomura when he planned to withdraw from the academy, determined to remain by his side and confess her love.

Mary Kikakujou
Rin and Mary share a professional relationship as fellow members of the Supreme Five Swords. Both initially held strong disdain for men and enforced the academy’s rules with equal severity. While they respect each other’s abilities, their shared romantic interest in Nomura often causes friction. Rin disapproves of Mary’s more overtly provocative behavior toward Nomura, which she finds both irritating and threatening.

Despite this rivalry, the two are capable of cooperation when necessary. They have fought together against formidable opponents, such as Kirukiru Amou, and their teamwork was noted to have improved through Nomura’s influence, though occasional tensions remain when their affections for him resurface.

Mozunono Nono
Mozunono is Rin’s loyal subordinate and admirer, often supporting her unconditionally. Although Rin can be blunt toward her—at times even calling her an “idiot” their relationship is portrayed as strong and mutually supportive. The two share a common background in swordsmanship, as seen when both used the Crane Stance during their battle against Nomura, suggesting they trained under similar instruction.