Sayo

Sayo is a minor character of Demon Slayer: Kimetsu no Yaiba. She was one of the orphaned children that Gyomei Himejima raised in a temple before he became a Demon Slayer.

Appearance
Sayo has black, short hair styled in a blunt bob with a fringe. During her time at the temple, she typically adorned herself in a traditional kimono embellished with delicate floral patterns. Like the older children, she did not wear any shoes.

History
After losing her parents at a tender age, Sayo found herself in the care of Gyomei within the sanctuary of a temple. There, she was embraced by a new family, comprising of nine other orphaned children, who became her steadfast companions. Bound not by blood but by shared experiences and a sense of belonging, they forged a deep and unbreakable bond.

In a moment that would forever haunt her memories, a night of tragedy unfolded within the temple walls. Sayo was four years old at the time, when the harmony of their sanctuary was shattered by an act of disobedience. Kaigaku, one of the other children, ventured beyond the boundaries set by the temple, and was accosted by a demon, and in a desperate bid to save himself, betrayed his companions. When darkness descended, the child extinguished the protective Wisteria Incense and invited the demon into the temple. Four children immediately fell victim to the demon's relentless assault, while the remaining ones defied Gyomei's orders and were killed while they fled. Amidst the chaos and despair, Sayo alone remained, huddled in a corner, tears streaming down her face. Determined to protect her at any cost, Gyomei fought hard against the the demon until the sun rose.

Eventually, help arrived. In her state of shock, Sayo exclaimed: "That man is a monster! He... killed everyone!", referring to the demon that infiltrated the temple. However, with the demon's remains disintegrated by the morning sun and only the children's lifeless bodies remaining, the villagers misunderstood Sayo's words and wrongly attributed the murders to Gyomei. Sayo, still traumatized by the incident, struggled to articulate herself properly and failed to dispel the suspicions that had befallen Gyomei, causing him to be unjustly imprisoned and charged with the heinous crime of killing the eight children. It was only through the intervention of Kagaya Ubuyashiki that Gyomei was released before facing execution for crimes he did not commit.

The weight of guilt rested heavily upon Sayo's shoulders, burdening her soul with the memory of Gyomei's wrongful arrest. Even as a decade has passed, time's passage did little to ease the ache within her heart. She longed for the opportunity to seek forgiveness and offer her heartfelt apology to the one who had selflessly protected her. However, the chance to mend the past eluded Sayo as she never saw Gyomei again before he died in the final battle against the demons.

Hashira Training Arc
Upon completing all the assignments given by Gyomei during the Hashira Training session with him, the Stone Hashira acknowledged Tanjiro Kamado's dedication and accepted him as a worthy individual. Reflecting on his experience raising Sayo and the other children in the temple, Gyomei contemplated the inherent nature of children — pure and innocent yet vulnerable, prone to falsehoods and capable of displaying cruelty and selfishness. However, upon observing Tanjiro's unwavering honesty and integrity, Gyomei could tell that this boy is truly different and told him his story with the children in the temple. Moved by the story's outcome, including Sayo's heartbreaking betrayal, Tanjiro's tears flowed uncontrollably. In an act of comfort, Gyomei gently patted Tanjiro's head, reminiscent of the affection he had once bestowed upon Sayo.