Kaoru's father is an alcoholic who physically and verbally abuses his son, directly blaming Kaoru for the accidental death of his daughter Karen. During drunken rages, he accuses Kaoru of responsibility for Karen's death, demands he bring her back, and even suggests Kaoru sacrifice his own life in exchange. The family fractured after Karen's death, resulting in his wife leaving and severing contact. He neglects Kaoru's well-being, fostering an unstable and hostile home environment. This neglect extends to his sudden announcement of plans to remarry and relocate to Tokyo with a new partner, expecting Kaoru's unquestioning acceptance without regard for his feelings or attachments. His actions significantly contribute to Kaoru's trauma and pervasive sense of guilt.

The character exhibits no meaningful development or redemption. His attempts at reconciliation following violent incidents are superficial and quickly withdrawn if Kaoru doesn't respond as desired, revealing a cyclical pattern of abuse devoid of genuine remorse. His fixation on the past and inability to process grief healthily perpetuate the family's dysfunction, leaving a lasting negative impact on Kaoru's emotional state.