Genya Shinazugawa suffered under an abusive father in a family of seven. His mother shielded the family, earning Genya's profound admiration. After their father's murder, Genya and his older brother Sanemi vowed to protect their siblings. Tragedy struck when their mother vanished; Sanemi searched while Genya guarded the younger children. A demon—later revealed as their transformed mother—attacked, killing four siblings and scarring Genya's cheek. Sanemi intervened, hurling the demon out and ordering Genya to flee. Discovering Sanemi standing over their mother's dissolving body, Genya wrongly accused him of murder, creating a lasting rift. Genya initially displayed a foul-mouthed, ill-tempered personality, rejecting help and acting aggressively. During Final Selection, he grabbed Kanata Ubuyashiki's hair and yelled, provoking Tanjiro Kamado to break his arm. His abrasive nature mirrored Sanemi's. Over time, particularly battling Upper Rank Four Hantengu alongside Tanjiro, Nezuko Kamado, and Mitsuri Kanroji, Genya learned cooperation. This softened his interactions, making him more sociable, though he occasionally relapsed—like punching Zenitsu Agatsuma for insulting Sanemi. His core motivation remained reconnecting with Sanemi, whom he revered as "the nicest person in the world." Unable to use Breathing Styles, Genya compensated through unique physiology: unnaturally strong jaws and specialized digestive organs let him consume demon flesh without fatal consequences. This granted temporary demonic traits—fangs, darkened sclera, yellow-tipped hair, enhanced strength, rapid regeneration, and heightened senses. The potency varied with the demon consumed. Eating part of Hantengu's clone Aizetsu let him overpower the Upper Rank, while consuming Kokushibo's flesh sword unlocked the Blood Demon Art Vampiric Trees, generating binding trees from flesh bullets fired via his altered shotgun. He wielded a Nichirin shotgun with specialized ammunition and a Nichirin wakizashi for close combat. He used Repetitive Action, chanting prayers from the Amida Sutra, to focus his mind and endure pain, taught by Stone Hashira Gyomei Himejima. Genya's actions were defined by his relationship with Sanemi. Realizing his mistake about their mother's death, he joined the Demon Slayer Corps seeking forgiveness and recognition. Sanemi, now Wind Hashira, repeatedly rejected him, threatening violence and denying kinship to shield Genya. During Hashira Training, Sanemi berated Genya's inability to use Breathing Styles and demanded he quit. Genya desperately confessed his taboo practice of eating demons for acceptance. His loyalty persisted even when Sanemi attacked Tanjiro for defending him; Genya pleaded for Tanjiro's safety. In their final battle against Upper Rank One Kokushibo, Genya sacrificed himself by consuming Kokushibo's hair and flesh sword to aid Sanemi and Gyomei. Mortally wounded and disintegrating, his last words prayed for Sanemi's prosperous life, expressing gratitude and love. Genya survived major conflicts like the Swordsmith Village battle against Hantengu, where his demon consumption proved pivotal. However, during the Infinity Castle arc, Kokushibo bisected him horizontally. Consuming Kokushibo's flesh let him regenerate and immobilize the Upper Rank with his Blood Demon Art, facilitating Kokushibo's defeat but leaving Genya fatally wounded. Turning to ash, he achieved reconciliation as Sanemi acknowledged their bond. Genya succumbed to his injuries in his brother's arms.