Kirukiru Amou is a female transfer student to Private Aichi Symbiosis Academy following her role in a large-scale brawl. She possesses long black hair reaching her knees, dark brown eyes, and a curvaceous figure. Her standard attire is the academy uniform: a cropped blue blazer, off-white button-up shirt, blue skirt, red tie, stockings, and black boots. She occasionally wears casual clothes: a purple short-sleeved shirt with a belt and a white skirt slightly above the knees, still paired with stockings.

Her personality exhibits deranged psychopathy centered on an obsessive fixation on her former acquaintance, Nomura Fudou. This manifests as classic "yandere" behavior, including extreme jealousy and a readiness to harm or kill anyone perceived as obstructing her connection to Nomura. She displays cruelty, condescension towards those she deems inferior, and a compulsion to dominate others, particularly evident in her fixation due to Nomura's refusal to submit. Interactions involve disproportionate retribution, like nearly killing a student Nomura befriended simply because Nomura had plans with him.

Before Aichi Academy, Amou attended another school where her relationship with Nomura originated. She fought him there, inflicting severe injuries that hospitalized him and left a scar on his back after piercing his chest following his rejection of her demand to become her "man". At Aichi, she earned the title "EMPRESS" after single-handedly defeating two members of the school's elite combat group, the Supreme Five Swords (Onigawara Rin and Kikakujou Mary). Witnessing a kiss between Nomura and Onigakawa Rin escalated her jealousy, reinforcing her worldview.

As punishment for instigating chaos at Aichi, she transferred to Hokkai Academy. Before departing, she kissed Nomura, an action that left a lingering emotional impact on him, later depicted in an OVA where he dreamt of her while choosing companions for a hot springs visit.

Amou is a master of Uechi-Ryu Karate. Her abilities focus on precision strikes capable of tearing flesh, breaking weapons, and effortlessly killing opponents or large animals like bears. Her signature technique is the "Auto-Counter," instinctively hardening her fingers to slash or stab opponents pre-emptively or in response to attacks. Variations include Tiger’s Claws (slashing), Pickaxe Fist (stabbing), Four-Speared Hands (a piercing attack that penetrated a manga magazine Nomura used as a shield), Tegatana (Okinawan Karate/Aikido-based strikes allowing her to punch concrete, break iron, and pierce bears), Foot Blade: Two-Sided Kick (simultaneous kicks to multiple targets), and Roundhouse Block (dual-handed defensive rotation).

Rigorous training granted her enhanced physical attributes: Strength sufficient to overpower skilled fighters like the Supreme Five Swords; Speed exceeding most Supreme Five Swords members and Nomura, enabling effective Auto-Counters; and Durability allowing her to harden her body at will, rendering most slashing/piercing attacks ineffective (described as skin "hard as steel" and muscles "hard as concrete"). This durability offers less resistance to blunt-force trauma, exemplified by vulnerability to Nomura’s Spirit Bullet technique.

Her dynamic with Nomura remains central, evolving from violent enmity to a complex, unresolved connection underscored by physical confrontations and her transfer. She serves as a foil to Nomura, contrasting his desire for freedom with her obsession for domination.