Kate is a skilled assassin and expert sniper whose formidable abilities are honed under the watchful eye of her mentor and handler, Varrick. Orphaned as a child, Varrick became her father figure, providing her with extensive training in weaponry and combat techniques, ultimately integrating her into his elite team of covert operatives.
The film begins with Kate in Osaka, preparing for a critical mission to eliminate an officer within a powerful yakuza syndicate. As she takes her position with her rifle, her target steps out of his vehicle but surprises her by being accompanied by a child. Against her better judgment, Kate is compelled to follow Varrick's orders and completes the mission, but this decision haunts her, igniting inner turmoil as she struggles with the violation of her personal code against killing in the presence of innocents. Though successful, she decides to carry out one final mission before retiring for a fresh start.
Before she embarks on this last assignment, she encounters a charming stranger named Stephen at the hotel bar, where they share a bottle of wine and spend the night together. However, as she prepares for her mission, Kate experiences disorientation, causing her to miss a crucial shot. In a shocking turn of events, she realizes she has been poisoned by Stephen, awakening in the hospital to the grim revelation that she has acute radiation poisoning from Polonium-204, leaving her with only twenty-four hours to avenge herself.
Fueled by betrayal, Kate steals stimulant drugs and a firearm, setting out on a revenge-fueled quest to hunt down those responsible for her poisoning. She tracks down Stephen and learns he and his girlfriend were coerced into the act by Sato, a yakuza associated with the Kijima crime family. Determined, Kate locates Sato at a high-end restaurant and unleashes her wrath, eliminating him and numerous armed yakuza members in a relentless Shootout.
In her pursuit of the elusive boss, Kijima, Kate kidnaps Ani, Kijima’s biracial niece, realizing that Ani witnessed her father's murder during the Osaka mission. Although initially intending to use Ani as bait, Kate's protective instincts kick in as she discovers that Ani's own family is intent on her destruction, orchestrated by the unscrupulous advisor, Renji.
As she delves deeper into the conspiracy, Kate starts to question her loyalty to Varrick after acquiring chilling information revealing a deal between Varrick and Renji. This collusion involved the incorporation of Varrick's team into the syndicate in exchange for the eradication of Kijima and his entire lineage. With time running out, Kijima generously offers Kate an armed force to assault Renji's stronghold.
What follows is a harrowing gunfight where Kijima’s forces annihilate Renji’s men. In an act of poetic justice, Kijima personally beheads Renji for his duplicity. The climax culminates when Kate finds Varrick holding Ani at gunpoint. In a tense showdown, the two exchange gunfire, resulting in Varrick being mortally wounded. With Ani's support, Kate ascends to the roof, finally reconciling with her tumultuous past, where she peacefully succumbs to her fate.
