Giyuu Tomioka

His family was killed by demons, and he was orphaned along with his older sister, Tsutako. Tsutako later sacrificed herself to protect him, leading Giyu to become a demon slayer, eventually becoming the Water Pillar. He also grapples with survivor's guilt related to his deceased friend, Sabito, who died during their training. Detailed Breakdown: Orphaned and Grieving: Giyu and Tsutako were orphaned after their parents died, likely from illness, and lived on their family estate. After Tsutako's death, he tried to tell others she was killed by a demon, but was labeled mentally ill. Sacrifice and Transformation: Tsutako sacrificed her life to protect Giyu from a demon, a pivotal moment that led him to dedicate himself to becoming a demon slayer, according to Tokyo Otaku Mode. Training and Loss: Giyu became a disciple of Sakonji Urokodaki and trained alongside his friend Sabito. However, the loss of Sabito during the Final Selection, where only the strongest survived, deeply affected him, leading to a period of depression and a desire to suppress his emotions. Survivor's Guilt: Giyu feels a strong sense of guilt for surviving the Final Selection while Sabito died. This guilt and the loss of Tsutako contribute to his reserved and emotionless personality. The Water Pillar: Giyu later becomes the Water Pillar in the Demon Slayer Corps, a highly respected position, but he continues to grapple with his past. Tanjiro's Mentor: He plays a crucial role in guiding Tanjiro and his sister Nezuko, who is also a demon, and ultimately helps Tanjiro on his path to becoming a demon slayer.