Kyo Sohma carries the curse of the Cat, excluded from the Chinese Zodiac. This curse transforms him into an orange cat if hugged by the opposite sex or under severe stress. Removal of his Juzu bead bracelet forces him into a grotesque, foul-smelling monstrous form embodying the Cat's vengeful spirit. His status as the Cat makes him an outcast within the Sohma family, subjected to lifelong discrimination, pity, and isolation.

Born to an unnamed mother and father, Kyo endured a traumatic childhood. His mother, terrified of his true form, isolated him and constantly monitored his beads. She suffered verbal and emotional abuse from his father, who blamed her for bearing the Cat. Unable to bear it, she committed suicide by jumping in front of a train when Kyo was young. At her funeral, family members, including his father, blamed Kyo for her death, fueling his deep resentment and self-loathing. Kazuma Sohma, recognizing the injustice, adopted Kyo, becoming his martial arts mentor and father figure. Kyo initially resisted Kazuma's care to avoid being a burden but grew to deeply respect him.

As a child, Kyo briefly befriended Kagura Sohma, who pitied him. Their friendship ended when she forcibly removed his beads, witnessed his monstrous form, and reacted with horror, intensifying his isolation. He also encountered Kyoko Honda, Tohru’s mother, who persistently engaged him despite his hostility. Kyoko shared stories about her daughter, sparking Kyo’s interest in Tohru. He once promised Kyoko he would protect Tohru but failed to save Kyoko during a car accident. Fearing transformation if he touched her, he hesitated, leading to her death. Her final words, "I’ll never forgive you," haunted him, fueling immense guilt. He repressed this memory and directed all blame onto Yuki Sohma, the Rat.

Kyo’s hatred for Yuki defined his adolescence. He saw Yuki as effortlessly privileged and dedicated himself to martial arts, determined to defeat him. Akito Sohma, the family head, exploited this rivalry with a bet: if Kyo beat Yuki before high school graduation, he would avoid confinement in the Cat’s Room; if he lost, he would be imprisoned there indefinitely. Kyo accepted, viewing victory as validation. He moved into Shigure Sohma’s house, clashing violently with Yuki. Tohru Honda’s arrival disrupted this dynamic. Her presence initially reminded him of his guilt over Kyoko’s death, but her genuine admiration for the Cat legend and persistent kindness gradually softened him. She became the first person to accept his true form without fear or pity.

Tohru catalyzed Kyo’s emotional growth. He developed romantic feelings but felt unworthy due to his guilt and curse. When Tohru confessed her love, he rejected her to protect her from his perceived toxicity. After Yuki and Tohru’s friends confronted him about hurting her, he faced his past. He confessed his role in Kyoko’s death to Tohru and apologized sincerely. His heartfelt confession to Tohru—"I want to be with you... because I love you!"—coincided with the breaking of the zodiac curse, freeing him from his transformations.

Post-curse, Kyo reconciled with Yuki, acknowledging their mutual envy and forming a tentative friendship. He became calmer, more empathetic, and openly affectionate. He and Tohru married and had three children: Hajime, another son, and a daughter. As an adult, Kyo worked as a martial arts instructor, maintaining a close bond with Kazuma. His son Hajime inherited his protective nature and struggles, echoing Kyo's path toward emotional openness.