Haruka's father, an office employee, became a widower when his wife died of a terminal illness. Grief drove him to bury himself in work, creating emotional distance from his daughter. This neglect left Haruka feeling undervalued and resentful, believing he had forgotten both her and her mother's memory.

He originally gifted his wife a hand mirror, which later became Haruka's cherished memento. After his wife's death, he failed to help Haruka process her grief, deepening her isolation. His absence and work preoccupation left her unsupported in longing for the lost mirror and her mother.

His character development unfolds indirectly through Haruka's experiences in Oblivion Island. Her journey of reconciling with forgotten aspects of her past, including confronting her neglected stuffed animal Cotton, fosters understanding of his coping mechanisms. This growth culminates in her calling him for dinner upon returning home—a step toward mutual reconciliation and renewed family bonds.

Unnamed and identified solely as Haruka's father, his background comprises his office occupation and emotional arc of grief and gradual reconciliation with his daughter.