Born beneath a crimson dawn, Tanjiro Kamado bore a striking mark: flame-like patterns of blood red on his left forehead, a mystery to all. Fate’s cruel hand led him to discover his family slaughtered by Muzan Kibutsuji, only his sister Nezuko, now a demon, remained. In a snow-laden forest, the Water Breathing user Giyu Tomioka confronted Nezuko. Tanjiro, shielding his sister, fought with desperate ferocity. Nezuko, against all demonic instinct, spared him. Moved, Giyu sent them to Sakonji Urokodaki. For two years, Tanjiro trained under Urokodaki and Makomo. Each night, Yoriichi Tsugikuni, the progenitor of Sun Breathing, appeared. Yoriichi taught not just technique, but the rhythm of life itself, breath entwined with heartbeat, motion with flame. Tanjiro honed his skills against lesser demons. Urokodaki revealed his mark as a lineage tied to dormant Sun Breathing users. At the Final Selection, Tanjiro avenged Urokodaki’s disciples against the Hand Demon, emerging as one of four survivors. His early missions, including the Swamp Demon and later defeating Arrow and Temari Demons with Tamayo and Yushiro, solidified his mastery of Sun Breathing. Alongside Zenitsu and Inosuke, he became an unbreakable trio, facing countless demon horrors. On Natagumo Mountain, he showed mercy to the Spider Mother and confronted Rui. Channeling the sacred Hinokami Kagura, he burned through Rui and the Spider Daughter. Giyu and Shinobu arrived, their presence igniting renewed conflict over Nezuko’s demonic nature. Giyu stood firm in their defense. When Kanao Tsuyuri attempted to strike, Tanjiro parried, not in aggression, but in protection. Where his crow leads him to the Hashira and their master who agreed to let him live. Tanjiro's strength was undeniable. He was eventually named Sun Hashira.

Months later The Mugen Train mission brought them alongside Flame Hashira Kyojuro Rengoku. They defeated Enmu and his dream demons. Then, Akaza, Upper Rank Three, appeared. The ensuing battle was devastating. Rengoku lost an eye. Tanjiro fought fiercely beside him, pushing Akaza to his breaking point before the demon retreated, battered. More time passed and, Tanjiro joined Rengoku and Tengen in the Entertainment District. They faced Daki and Gyutaro, Upper Rank Six. The fight pushed them to their absolute limits. In a moment of desperate resolve, Tanjiro Sun Mark flared to its full potential defeating the demons. At the Swordsmith Village, Tanjiro, Nezuko, Genya Shinazugawa, Muichiro Tokito, and Love Hashira Mitsuri Kanroji defended against Gyokko and Hantengu. Muichiro dispatched Gyokko. Tanjiro, Mitsuri, and Genya overwhelmed Hantengu. In the heat of battle, Tanjiro claimed a Bright Red Nichirin Sword, a blade that only responded to the wielder of Sun Breathing. Then, a miracle occurred. Under the sun's golden rays, Nezuko stood unharmed, and she spoke. Her mind, her soul, though still demon, was free. Not human, but reborn as Nezuko Kamado, Demon of the Demon Slayer Corps. Now, Tanjiro trains in his headquarters, Yoriichi’s voice a constant echo in his breath, his mark burning brighter. Sun Breathing flows through him like lifeblood. But Muzan has seen. Nezuko resists the sun—the very essence of demon fear. He desires her power. The Hashira Training begins, a crucial prelude. Back at Tanjiro’s headquarters, he sits in deep meditation, the spirit of Yoriichi a palpable aura, his breath a testament to the fiery path forged in unwavering devotion.