Chinatsu is a young woman who serves as the first and only female member of Orchestra, an international team of assassins. She appears as a primary antagonist during the Musica Ex Machina story arc. Her physical appearance is designed to give her a deceptive schoolgirl look, consisting of a light short-sleeved button-up shirt with a tie, dark gloves, a dark skirt, and dark socks and shoes. She has fair skin and shoulder-length hair, which in the anime adaptation is light brown, paired with light red eyes. One of her targets notably described her eyes as indicating that she was insane. She almost always wears a distinctive medium-colored slouch hat with three Xs on the front of the crown, a gift from her mentor Shisho, and she wears it with the side brims secured by the chinstrap.

Chinatsu was not always the cold-blooded killer she becomes. In the anime, her backstory reveals she was an ordinary girl attending an opera performance with her parents when Shisho, also in attendance, assassinated the prima donna before opening fire on the crowd with a machine gun. Her parents were killed trying to protect her. In a moment of shock and survival instinct, she picked up a pistol and shot Shisho in the shoulder. Rather than killing her, he was impressed by her act of defiance. He approached her while she still had the gun aimed at him, but she could not bring herself to fire a second time out of fear. Shisho then kissed her cheek and told her that the gunshot was a nice sound, an act that marked the beginning of her transformation.

Following this traumatic event, she was taken under Shisho's wing and trained to become a highly skilled assassin. Her personality underwent a dramatic change as she accepted Orchestra's artistic philosophy that they bring death to their targets. She grew to enjoy killing, often licking her lips in anticipation of a kill. Her psychological dependence on Shisho is deeply complex and displays elements of Stockholm syndrome. While she remains fiercely loyal to him in the field, she also harbors a deep-seated resentment for how he destroyed her former life. This internal conflict becomes most apparent after his death, when she berates him for ruining her life while simultaneously weeping over his loss and swearing vengeance on those responsible.

One of Chinatsu's most peculiar and defining characteristics is her superstition regarding accuracy. During her first mission with Shisho, they had to cross a river to reach a target. Uncomfortable with her wet clothes below the waist, she secretly removed her underwear. She performed exceptionally well that day, killing more people than Shisho, who praised her for it. From that point forward, she developed the belief that going without underwear increased her shooting accuracy and consequently refused to wear any during missions. A target who discovered this interpreted it as a perversion, but for Chinatsu, it is purely a tactical superstition.

In her role within the story, Chinatsu and Shisho are hired to assassinate the arms dealer Koko Hekmatyar in Dubai. Unlike her mentor, who tends to become consumed by the chaos of battle, Chinatsu maintains a much cooler head in combat. She possesses excellent instincts and exceptional situational awareness, which allows her to rein in Shisho's more uncontrollable tendencies and makes the pair a formidable combination. When she confronts Koko, she grabs her wrist and demands to know why she sells weapons even though she knows it will ultimately lead to death. The conversation leaves Chinatsu unsettled, and she comes to strongly dislike Koko. Her hatred only intensifies when she realizes that the young boy Jonah, whom she had earlier thought was cute, is actually protecting Koko. During the ensuing gunfight, she notably deflects Shisho's aim when he has a clear shot at Jonah, claiming that the boy was too cute to kill.

Chinatsu is highly acrobatic and proves to be a difficult target to hit, even when multiple skilled opponents are firing at her. Her primary weapons are pistols, but she also wields a distinctive single-shot 40mm grenade launcher known as the Chinatsu Cannon Special. Beyond her combat skills, she has become proficient at rigging weapons, such as pistols with timers, in ways designed to deliver the maximum possible pain to a target before death, showcasing a cruel and methodical creativity. She is also fluent in Italian, a skill she uses to communicate with Shisho in the field.

After Shisho is killed by Lutz during the confrontation with Koko's team, Chinatsu is completely unhinged by the event. She becomes so distracted that she wanders into the line of fire, although her opponent hesitates to shoot a young woman. After managing to escape, she shifts her focus entirely to revenge, determined to finish Orchestra's original mission and assassinate Koko. When Koko later finds her and offers her a place on the team, Chinatsu adamantly refuses, admitting she can never forgive Koko for killing Shisho. The pursuit of revenge ultimately leads to her own death when she is mortally wounded by a sniper.