Kaoru Yoshikawa is a young girl who serves as the central character in the Tombstone Village story featured in the anime. She is introduced through a visit to a remote and peculiar village during summer vacation. She has an older brother named Tsuyoshi Yoshikawa, who drives her to the village at the invitation of her friend, Izumi, who had moved there the previous year. The journey takes a catastrophic turn when Tsuyoshi accidentally hits a young girl with the car. Kaoru is the one who checks the victim for a pulse and ultimately pronounces her dead, an act that immediately burdens her with a profound sense of guilt.

This guilt shapes her entire personality throughout the narrative. Kaoru is defined by a strong internal moral compass that clashes violently with the circumstances she is thrust into. Unlike her brother, she is immediately horrified by the accident and wants to take responsibility, repeatedly insisting that they should confess to the authorities. Her primary motivation is to do the right thing and alleviate the crushing guilt she feels, but she is consistently overruled by the stronger will of her brother. When she learns that the victim was her friend Izumi's younger sister, Ayumi, her emotional state deteriorates further, leading to a complete breakdown when Izumi discovers bloodstains in their car. Despite being an unwilling participant, Kaoru is ultimately too passive and intimidated by her brother to defy him, which forces her to assist in the cover-up, including the disposal of Ayumi's grotesquely petrified body.

Within the story, Kaoru plays the role of the conflicted moral center, a witness to horror who is powerless to prevent it. Her most significant relationship is with her brother, Tsuyoshi. He is the dominant figure who makes all the decisions, forcing Kaoru to comply with his plan to hide the body and remain silent, even as Izumi gives them multiple opportunities to confess the truth. Her relationship with her friend Izumi is one of profound betrayal; by aiding in the cover-up, Kaoru participates in a lie that destroys her friend's family, even if she does so under duress.

Kaoru experiences significant psychological development, transitioning from a carefree girl to a person shattered by guilt and trauma. At the beginning of the trip, she is playful, teasing her brother about his crush on Izumi. By the end, she is reduced to a state of constant weeping and apology. The anime concludes with Tsuyoshi petrifying and dying from an injury sustained while disposing of Ayumi's body, leaving Kaoru alone to weep, tormented by the guilt of her inaction as Izumi’s entire family is revealed to have committed suicide. The anime ending focuses on her emotional devastation. In a different version of the story found in the original source material, her development takes a slightly different turn, culminating in a decision to finally turn herself in to the police, only to arrive and find that Izumi’s family has already taken their own lives. Kaoru does not possess any notable supernatural abilities; she is an ordinary human caught in an extraordinary and horrific situation.