Kazuo Miyaura, the late father of protagonist Momo, anchors the narrative’s emotional core through his absence, his death preceding the story as a catalyst for her journey. An oceanographer consumed by his work, he perished in a boating accident during a final research expedition—hours after a heated argument with his daughter over missed family commitments, leaving her burdened with unresolved guilt. His incomplete letter, found with only the salutation *“Dear Momo,”* haunts her as a tangible remnant of their fractured connection, its unsaid words echoing his lifelong struggle to voice private emotions despite his eloquence in scientific writing. Colleagues and loved ones remembered him as a gentle, introspective soul, “one of the rare good ones,” yet his wife observed how professional precision clashed with personal reticence, deepening Momo’s uncertainty about his true feelings.

A mirrored heirloom gifted to his wife early in their marriage symbolized their bond until its shattering by a spectral force, intertwining supernatural intrusion with familial fragility. Posthumously, Kazuo’s hidden message of pride surfaces during a lantern-floating ritual honoring the dead, bridging his silent love with Momo’s acceptance. His legacy lingers in themes of fractured communication, the weight of unmet expectations, and love persisting beyond words, ultimately guiding his daughter’s reconciliation with loss and the ghosts of what went unspoken.