Kanao Tsuyuri suffered severe childhood abuse that rendered her emotionally withdrawn and incapable of independent decisions. Sold into slavery, she was rescued and adopted by Kanae and Shinobu Kocho at the Butterfly Mansion. To help Kanao manage her paralyzing indecision, Kanae introduced a coin-flipping ritual. Despite appearing passive, Kanao independently mastered Flower Breathing by observing her adoptive sisters and joined the Demon Slayer Corps without permission, emerging unharmed from Final Selection. She became Shinobu's Tsuguko, training rigorously to develop exceptional physical strength, speed, reflexes, and observational skills enabling her to predict opponents' movements. Initially acting mechanically on orders, such as pursuing Nezuko Kamado on Mount Natagumo under Shinobu's directive, Kanao experienced significant development through interactions with Tanjiro Kamado during Rehabilitation Training. After repeatedly defeating him in reflex games, Tanjiro borrowed her coin, declaring he would flip it until landing on the outcome where she would "listen to her own heart," challenging her dependence on external validation. Later, in the Entertainment District Arc, she actively defied the Sound Hashira Tengen Uzui to protect Aoi and Naho from mission recruitment, marking her first major independent choice inspired by Tanjiro. When Tanjiro awoke from a coma post-arc, Kanao dropped a vase in shock and tearfully expressed relief, revealing growing emotional capacity. The Infinity Castle Arc triggered Kanao's most intense transformation. Witnessing Upper Rank Two Doma kill and consume Shinobu ignited overwhelming rage, causing her first emotional breakdown. Fueled by vengeance for both Shinobu and Kanae (previously killed by Doma), she verbally taunted him about his emotional emptiness during their fight. She deployed Flower Breathing's Final Form: Equinoctial Vermilion Eye, enhancing her vision by concentrating blood flow to her eyes at the risk of permanent blindness. She cooperated with Inosuke Hashibira, warning about Doma's poisonous ice crystals and coordinating attacks. After beheading Doma, she found Shinobu's broken butterfly hairpin and wept openly, contrasting her inability to cry at Kanae's funeral. The technique's backlash destroyed vision in her right eye. In the final battle against Muzan Kibutsuji, Kanao fought alongside other Demon Slayers despite her injury. After Muzan's defeat, observing Nezuko's desperate attempts to reach the demon-transformed Tanjiro, Kanao remembered Shinobu's vial of human-conversion medicine. She sacrificed her remaining vision by injecting it directly into Tanjiro, successfully reverting him without hesitation, demonstrating complete emotional independence. Following the war, Kanao married Tanjiro Kamado and became a doctor. She lived a full life, eventually passing Shinobu's hairpin down to her descendants, including her great-grandson Sumihiko Kamado.